When you close a LN channel, some of the coin belongs to you, and some belongs to the other party to the channel. If the other node does not want to potentially wait days to access their coin, it will not sign a cooperating closing tx with a low fee. If the other node is not cooperating and you want to unilaterally close the channel, you must use a previously signed tx, including whatever fee rate was set.
I'd like to see older channel states but Eclair doesn't show them. I guess I'll have to dig into the backups made on Google Drive for those?
As a proof of concept, it would be interesting to see if I could actually use an older transaction to steal funds (and if I succeed give them back to the node, but that's not the point here). I currently have a channel (opened by me) with only just over 3000 satoshi on my side. If I'm the only one paying for fees, I don't expect any of this money back in my wallet. But even all of it is used as fee, it won't be a high fee. So: what if I wait until fees go up, then close the channel, which won't confirm, and after the right amount of time, I broadcast an older state (which at the time might have been signed with a higher fee)?
It's still a mystery to me how the older signed transactions would work, given the fact they can't be broadcasted instantly but only a certain amount of time after trying to close the channel.
You are highlighting a flaw in the concept of LN. If one side is due to receive only a small amount of coin upon closing the channel, they may not stand to lose anything by broadcasting an old channel state, and if the old channel state is going to result in the other node loosing a small enough amount of money, they may not broadcast the "penalty" transaction that allows him to receive all of the coin in the channel.
No wallet software is going to make it easy for the user (nor should they) access to old channel states because of how easy it is for the other node to take all the money in the channel, resulting in you loosing money. You would need to look in backups to find old transactions to close the channel in an outdated channel state.
I think you are also misunderstanding how the closing of LN channels occur. When you unilaterally close a LN channel, two transactions must confirm, an intermediary transaction and a final transaction. Say for example if you and I had an open LN channel, I was offline, and you wanted to close the channel. You would broadcast an intermediary transaction that is specific to the channel state. If the intermediary transaction is for an old channel state, it would expose information that would allow me broadcast a "penalty" transaction that allows me to receive all the coin in the channel, and if it is for the current channel state, it would expose useless information. After the intermediary transaction has x number of confirmations, you can broadcast the final transaction that results in coin going to each of us according to the channel state. If I didn't want to wait, I would have the option to broadcast the final transaction before the intermediary transaction has x confirmations -- the two final transactions both result in each of us receiving the same amount of coin, however they are two distinct transactions. If you are broadcasting an intermediary transaction associated with an old channel state, I would have x blocks to get the "penalty" transaction confirmed, including via the use of a CPFP transaction with a very high fee if necessary.
2) Creating inbound channel even harder
It's not as difficult as you think. Some nodes automatically open a channel back if one opens a big enough channel to them. There are also services from which you cant rent the inbound capacity.
Renting inbound capacity is a cost, and those services typically charge a flat fee attributable to a tx fee, and a percentage of the inbound capacity. This cost reduces the benefit to using LN.
