That's obviously a typo error.
He meant: "Isend can't send any bitcoins......" and everyone here gets it 

That's the link to the original article, is it the vice versa? Coindesk Author(s) have copy-pasted a content from Bitcointalk?
In my opinion, if they do, the forum doesn't have the authority to accuse the website, only the member who've posted the original contents can file an accusation since he's considered the Author of that post.

If it is the usual copied from that website and pasted to a Bitcointalk thread (no sources/quotes), use the "report to moderator" button to perma-ban the user.

So, you scanned the address and imported it to your phone... it just created a watch-only wallet.
You can't use that watch-only Mobile Electrum to spend those coins.
It's basically the same with seeing it on a blockexplorer, except you can make a transaction with it but you can't sign and broadcast it, make sure to keep your PC version and SEED written and stored somewhere safe.

If you wish to use the mobile version alone, you have to import the SEED from the PC wallet to your mobile using the "I already have a SEED" option in the create wallet menu. (You can make 2 or more wallet files in Electrum)

Considering the transaction fee and the mempool, that will gonna take a week or more to get confirmed.

In the history tab, is it being displayed as "Unconfirmed [rbf --------------]"? with the "rbf", it's possible to increase the fee even you've used "max" button when creating the transaction.
I've done rbf to a no-change transaction using Electrum before and it went fine, it just decreased the amount sent.

How it was posted? Like copy-pasted the article without any links to the source or a part of it quoted with a link to the website?
If it was posted like the poster's claiming that it is his words (no source link or quote), that's plagiarism and falls under rule #33.

This quote is self explanatory:

I'm not a mod but a regular reporter.

Then, you can't use ChildPaysForParent (CPFP). FYI, the balance will reflect after 3-6 confirmations.

What was the wallet that you've used to send the transaction?
If you're lucky enough and using a wallet with a turned-on ReplaceByFee (RBF) by default, do a RBF to the transaction in the history (for the sender).

Also, consider changing the fee estimation from "blocks" into "mempool" (ex. 1mb from tip) since I find it more accurate and reliable than block estimation.

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Additionally, if you're planning to use viabtc's accelerator, make sure to time the submission at exactly "Hour o'clock" (ex. HH:00) or few seconds after since they only accept 100 tx every cut off/hour and your tx fee must be 10sat/byte or more if it contains a SegWit address.

I thought that there was a a serious security issue with this extension?
If you follow the link above (post), they've mentioned about a vulnerability or sort of malicious code exposed by one of their employee.

Here's the exact post with that warning: Shop directly on Amazon.com with Bitcoin Post#21

After that, I never heard of this extension's name, until now.

Maybe something to do with the linux's root access?
But it's weird that it "partially worked" for Claire927, it generated/displayed 9 more addresses: 29 from 20.

But I'm sure, If you're using Windows, you don't have to use the second command for the gap_limit setting change to persist.

For BCH: Newer services depreciated the user of "1" addresses of Bitcoin Cash and only accepts "q" addresses by deafult , there's an option for legacy addresses though.
Bitcoin: Bitcoin doesn't support "q" addresses and you wont be able to continue if you ever pasted a BCH address.

If ever you mistakenly sent your precious Bitcoins to a trash wallet, knowing the private key is enough to be able to recover your bitcoins.
Read the comments above for some of the examples.

There's no issues regarding bc1 address to legacy address transactions.
Vice Versa has a problem if the wallet/exchange hasn't been updated to support native SegWit addresses.

Here's one for example: 7242816901983a5fe62d937ccc0581ae2711f8ed275d8cf7c695d0b930c553a4

I can't think of anything other than OP is trying to solo mine Monero or opening his own pool.
BTW, Just like Bitcoin and Ethereum, Monero also requires a fully synced node before you can start mining.

Unless he's not informed about mining pools, the only valid reason to mine using a full node is "solo mining".
@bitbadger for DYOR purposes, Check the selection of pools here, there are info and links to their sites too if you need more info.

Yes, if he really need to send it right now.
Though the fees will be extremely huge for any transaction amount specially if it's a bit urgent (@10-20sat/byte).
But it's better to consolidate the inputs now (1sat/byte is possible) before attempting to send anything to save fees.

So, if he's not in a hurry, he should consolidate first.

@superbotolo Whatever this is, do not download it!
The latest rar file was just uploaded in GitHub today without any pull requests/merge to review.

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Also, do not entertain any PMs requesting you to install/download an app or asking for your wallet.dat.
Like djhomeschool said, a simple pre-installed notepad app is enough to tell if it is BitcoinCore's wallet.dat or not.

Even an established member can tell: Removing the referral link to the post will lift it out of that specific rule.
There shouldn't be any problem as long as you're paying the referrals with Bitcoins.

100 transactions per person is too much to handle, imagine 100 persons using this as a "commercial" accelerator, that's about 10,000 transactions to queue. Users wont do that for sure and will just submit 1-5 tx each but the number of users who use their free service could reach millions.
BTW, 0.0001BTC/KB is the same as 0.00000010BTC/byte (10sat/b)

Here's a simple calculation:

• The maximum number of transactions you can fit to a block is 4,000 disregarding the transaction's sizes, so we will use the average 2,500.
  
• The average number of blocks per hour is 6
  
• 2,500 x 6 = 15,000 transactions per hour.

Ain't enough for 10 thousand users alone, talk about maximum of 100 each.

And if it's 100 per person every hour, why does it always rejects my very first 10sat+/byte tx at Hour:10 and above?  
But they always accept my 60+sat/byte transaction regardless of the minute.

Addresses are just derived from the private keys that were stored in the wallet.dat and if you load it to Bitcoin Core, those will be derived as bitcoin addresses no matter the compatible source wallet is.
However, there are transactions in the history shown in bitcoin blockexplorers.
Though most of them are "null" and can't be OP_Return, there is indeed a "history".

Good, there's high a chance that it's a Bitcoin Core wallet.dat 

No, if you investigate the transaction timestaps and his posts, it all happened within a short period of time after that "invalid logins".
Which could mean that he was phished (4/16 @OP) and immediately later, the hacker made a withdrawal
(2019-04-16 18:05:33 @35bfafb9a2bfd7873ca31782996a9c74dd346cca9f610a4e42f27233422da1a2) then, deleted his account right after the withdrawal which makes it invalid to the original site.

Then he created a new account the next day to contact support and the conversation is in the OP ("deleted yesterday" not quoted).

Nothing, once he closed the session, all sensitive data will be deleted, including the browsing history.

But it's pretty obvious that he's phished by a fake URL since he mentioned about "login details are not working" and it shouldn't happen in the first place unless there's a consistent typo on his several tries.

Like HCP, I also suspect that you've opened a different wallet file and didn't noticed the name in the title bar.

Open the "wallets" folder inside the ~/.electrum directory (default) and check if you have more than one wallet files.
Or do as HCP said, File->Open since it will open the directory where the last opened wallet was located.

If you're storing your wallet file in different locations or opened a wallet that wasn't in the default directory, browse to the default location manually.

Quoting myself here since OP somehow ignored the fact that it may be an Altcoin wallet.dat that's compatible with Bitcoin core like Litecoin and DogeCoin.

One transaction in the history is enough to tell that it's an altcoin wallet.dat or not (Forks may be harder to tell though).