This message from Shelby is very interesting. The issue is even more complex than what I believe it was.
No it's not. He seems like a nutjob. It's incredible that anyone is still going on about an "anyone-can-spend" attack. He obviously deeply misunderstands the incentives at work in Bitcoin.
No one cares what miners want; they will simply follow what users want. The lead-up to the Segwit fork proved that much. If miners switch to a fork where they steal everyone's coins going back 2012, nobody is going to switch to the miner's fork, LOL. Why would they? Clearly these are dishonest miners who are useless in securing a protocol.
Again, miners follow users, not the other way around. Without users, there are no transaction fees and no speculative value based on future usage. Miners will be spending massive amounts mining a completely worthless chain.
Just like they fell in line with Segwit activation, they will quickly migrate back to the "Core" chain where the vast majority of users will be. No, a bit of temporary congestion and slower block times won't cause anyone to fork to a chain where the protocol incentives obviously don't work to keep miners honest.
If the attack succeeded (LOL) it would only succeed in destroying trust in all the forks, and all of crypto.
Its interesting in the way that it could lead to a PoS version of bitcoin. If the miners betray the trust of users, and steal funds from Segwit adresses, the devs will fork it, rollback the theft, and use LN to validate blocks, since LN is dependable on Segwit. This would lead to a
PoS version of bitcoin.
On the other hand, we would have the Legacy mainchain keeping the same value of the forked one, due to being the longest chain in a PoW perspective (LN came only in 2017), which was not the case with BCH (which had less hashrate when it forked).
But Im probably wrong, since I dont know all the technicals about it.