You are not paying with Bitcoin.  You are holding Bitcoin in a third party wallet with a company that has the power to sell your Bitcoin for fiat money.

When you use your debit card at a merchant, TenX will spend fiat.  As soon as possible, they will sell your BTC for the amount of fiat that you spend (at a rate which they decide, usually a slightly worse rate than market rate so that they can make a profit), and they will subtract the amount of BTC that they sold from your balance.

So basically, it looks to the user like you're spending BTC, when in fact you're not.
They are intentionally vague about this, so they're probably giving you a bad exchange rate.  I personally use Xapo, and with them I can see their current exchange rate from my account at any time.

On normal Western home computers and normal Western Internet, it's still perfectly practical run full nodes.  It's not a significant problem yet IMO.  As long as people understand that full nodes are the way to retain a trustless wallet, they will continue to be fairly common alongside lightweight wallets for other purposes and some casual users.

The solutions are:

-Gradual onchain scaling (or rapid onchain scaling, depending on what you believe about the importance of full nodes), alongside common improvements in bandwidth and storage
-Efficiency improvements and optional onchain scaling solutions, such as SegWit
-Offchain solutions such as the Lightning Network.

Major BTC exchanges tend to have relatively high limits and the ability to raise those limits if you verify your identity very well and you contact them on the topic.

For example, GDAX accepts bank wires of $250,000.  You can also withdraw $10,000 per day and you can request higher withdrawal limits if necessary using an authorisation form.

You could trade large amounts on Gemini as well.

Occasionally, people will sell OTC if they find it particularly difficult to use these sites for any reason.  Especially the very rich people.

Yes, but major pools can support the SegWit2x chain at first, so that the legacy chain becomes inconvenient to use, which could help to push up the price of the new chain in the very short term.  Admittedly this would not have a lasting effect, but it's possible for much of that support to stay or for it to have a domino effect on further users.
I'm not sure I even believe that.  I strongly doubt that much of the money people have invested in BTC is invested with the intention of spending at merchants anymore.  Some of it is but I doubt it's the majority.

Looks like SegWit2x will be an alt, but a significant one which is accepted and sometimes supported by a variety of major services, so it'll at least not be irrelevant.

The chance of anyone's wallet generating them again is negligible, so as long as you don't use them again or tell anyone else to use them, they're pretty much gone.

TL;DR: yes.
Yes.
No.

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I was just clarifying with my previous post that you could choose to use the same seed in multiple wallets, and you would then be able to spend the same coins from both wallets.  But unless you make that choice, there is no connection between one wallet's seed and another wallet's seed.

The seed phrase is used to generate your public and private keys, which are linked to the addresses used to receive coins.
They could have.  You could choose to import your seed phrase from one wallet into another and use both wallets with the same seed if you wanted to.
Yes.
In theory, you could use the seed anywhere.  However, by doing so you would be exposing your coins to whatever you give the seed to.  That's why TREZOR recommends that you never type in your seed phrase anywhere on the Internet - because it's possible that an attacker could see it.  If you use your seed in a less secure wallet, your coins will be as safe as the weakest link, so to speak.
Yes.

Yes.  People spent billions of dollars orchestrating a massive market movement of several hundred dollars in an asset with a market cap of over $100,000,000,000.  Hilarious!

And they chose Halloween to do it too, a time that's known for joking around!

/s
What's the reason why it went anywhere above about $1000?  Minor pieces of news that are being used to justify a much more dramatic increase.  It's not like the transaction volume or even transaction capacity has increased that much, never mind actual adoption or usage by merchants.
It's surprising because at the same time somewhere out there a dog is on fire.

Well I suppose the most stable place it could get to is 0, because then there's no way for the price to go but up. 

For it to get relatively stable, it would have to go into a bear market and out of this bubble phase to a point at which most of the owners are relatively secure about the position.  In the last bear market (2015), this was around $200, and it was stable enough for a good year after that.

It's also possible that it would get stable if the price went up over a long and gradual rise.  However, this would require the price to be justified by genuine usage, otherwise it will always have the potential to continue being volatile and cause a lot of panic.

Even if it reaches that high, it might fluctuate similarly to how gold does - quite drastically, but over several years at a time.

Even if BTC's algorithm was ASIC-resistant, the vast majority of miners would be people who could afford huge investments in mining equipment, particularly in expensive GPUs in areas with low electricity.
I assume that by "developers" you mean "Bitcoin Core developers", because it's important to note that a significant number of people run clients other than the reference client.

However, this is entirely false.  If the Bitcoin Core client was altered in this way, people would have to choose to upgrade their client.  If people still run clients which involve having a max of 21 million coins and they continue the chain with a max of 21 million coins, there will still be a max of 21 million coins.
False.  Central bankers decide on the money supply, whereas what Bitcoin Core developers do (not that they have any intention of doing this), is ask people to support an increased money supply.  People could still choose to support the previous money supply and it would still exist.
There is a maximum block size to prevent more transactions from becoming a burden to full node users.  Miners are incentivised to reach the maximum block size with transaction fees.

No.  If you've sent it, you've sent it.  However, some wallets allow you to use Replace By Fee (RBF) in which you can replace your transaction with a new one that has a higher fee.  If you're using Electrum for example, you can decide to enable replaceable transactions.
AntPool and ViaBTC.
The same thing that you would do with any other wallet.

No.  Suggesting investments to people is a bad idea, especially when it's something so risky and volatile.  Whether or not they claim to be okay with losing their money in the worst circumstances, most people would care a lot if it went wrong and it would result in a lot of resentment towards you.  The effect of you making a suggestion which turned out poorly is much more serious than the effect of you making a suggestion that turned out well.
This is an extremely naive suggestion and is not based on any reasonable logic.  The price should be based on how BTC is actually doing, not rabid speculation.
To rephrase this into a good argument: "You can't use Bitcoin as a currency as much as you should be able to with a price as high as it currently is".  It's not that you can't use BTC, it's that a significant amount of holders don't.
 

Amazon doesn't remove the third party.  They have a lot of third parties - the additional sellers, the payments, and pretty much every aspect of their service.  There's less third parties to go into a shop and buy a product.
No one is focusing on that because they're too busy focusing on the price and getting caught up in the bubble.  They all convince themselves that it's different this time, when it's very much the same.

The price isn't the only indicator of adoption.  Adoption isn't going too well, whereas the price and the speculation is.

Any differences in price get arbitraged to death.  Their prices are going to be pretty much the same for practical purposes.  It's worth looking on coinmarketcap for trustworthy exchanges (none of them are that trustworthy, so be careful), but Bitstamp, GDAX and Kraken are a few that you could try.
If you want to pay with cash, you should probably try trading with someone in person (or with cash in the mail if you need to) on LocalBitcoins.
You're missing out bank transfers, which can be quite important.  Between cash and credit cards though, cash is ideal since it's non-reversible.  The risk of credit card fraud and necessary KYC regulations lead to a lot of complex verification which can be quite irritating.  

Credit cards are ideally for when you need a convenient way to pay online, but they can also result in high fees and annoying verification.

Sounds bad.  People very casually investing without really contemplating that much about it (just hearing about it on the phone and presumably hearing about previous prices) and not even learning how to invest themselves suggest that they have no idea what they're doing.

People also commonly say that a stock or asset is in a bubble when your grandmother is buying it.  The age range that they're talking about is people who are about 70, especially lay people.
What's this obsession that people have about "going mainstream"?  Can't it just be what it is, an experiment in cryptography, and then find out what it becomes used for?  Especially when the idea of "going mainstream" is just putting money in it, not actually doing anything with it.

Seems like quite an arbitrary statistic.  Not all power is produced using oil.

If you wanted to understand how many resources that mining Bitcoin takes up, you'd have to understand what power sources are most commonly used for BTC mining.  Presumably the most common is mains power, in which case you'd have to consider what percentage of mains power in different countries is generated by different power sources.

After that you'd have to alter your statistics based on the percentage of hashrate which is directed from different countries - something that's very hard to measure.

It's almost impossible to create accurate statistics of how many resources BTC mining actually takes up.  You could take the least efficient power source and say that mining 1 BTC takes up that many resources even though most power isn't created that way.

We don't know that.  There is no evidence of that.  They also haven't been mining at a loss at all yet, they've just been signalling their intention to mine the SegWit2x chain.

It will most likely involve mining at a loss if the current percentage of hashrate support stays the same and the current cost of futures matches the price when the chain is created, but you need to point out these assumptions to make a reasoned argument.
So you think that there's a non-negligible chance for a government to spend billions of dollars incentivising independent miners to individually mine at a loss, just so that the majority of BTC users would then choose to use a new Bitcoin client with a 2MB block size?
Once again, this is a very shocking assumption to make.  You'd need to justify it pretty well.

You should try explaining the importance of a Nash equilibrium in Bitcoin, in that when everyone acts in their own selfish interests, it benefits BTC.   

What's most important about this is that for the system to become insecure, huge groups of people (the economic majority) need to simultaneously disregard their own interests and work on something which is bad for them (and if this happens, they would still feel that it is good for them, since it's what they want to do).

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I like that you've written the blog like a conversation.  It works almost like an FAQ but in a structured and easy to understand way.

Fortunately, I have my seed in multiple different safe locations, so losing my seed doesn't really seem like a possibility to me.  Especially since I never carry it around with me.

Considering that most thieves don't have a clue what a TREZOR is, never mind how to steal the coins, I'd prefer having the information to take the coins relatively easy to find rather than it being somewhere that I'm likely to forget about and then lose access to my coins altogether.

I'll stay cocky until ten years or so from now when something goes wrong to put me back in my place.

Most of them did not support Bitcoin Cash.  Even BITMAIN didn't actively support Bitcoin Cash - they supported NYA earlier than that.  As for tolerating it, what else are you going to do?  Try and kill the developers?
They treat it that way because they don't perceive it to have enough support.  I don't see why this should prevent others from supporting it.

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Your other couple of points, though, seem quite reasonable to me.  I'll just be holding both chains and sitting back to see the show, personally.

Choosing to use SegWit is based on your belief about the merits of it (I decide to use it because I agree with the merits of it), but I wasn't intending to suggest that in my previous post.  I was intending to suggest that your belief in the importance of implementing SegWit as soon as possible should not interfere with the fact that a large number of customers using Copay will want a convenient way to move Bitcoin Cash and use it as they wish (or sell it if they do not believe in the merits of it).
Fair point.  I suppose they could have clearly pointed their users to that tool as an easier way of handling the situation, but they've still been at least moderately prompt on attempting to implement SegWit so I wouldn't treat them too harshly in that regard.
I'm not too sure either.  I think people need to distinguish between whether they would like to use BCH themselves (I personally don't use it) or whether they think other people will use it (I think that it has a significant amount of supporters).