I am confused as to whether I should be ashamed of myself. I don't understand this fundemental issue, but I also don't claim to understand Bitcoin. At least not at a cryptographic primitive level.
schnorr signatures solve the malleability problem
so how did segwit help lightning?
https://www.reddit.com/r/Bitcoin/comments/u9gya5/why_lightning_network_is_only_compatible_with/
by eliminating malleability
if bitcoin had schnorr signatures this would have been solved for lightning, and we'd still have 1Mb blocks, instead fo kinda 4mb blocks, but really still 1mb we promise
anyone who thinks they know about bitcoin who doesn't understand this most fundamental issue about the signature algorithm and segwit and lightning should be ashamed of themselves
Discussion
essentially it boills down to the problem that flipping a few bits of the transaction let you pass off a fake transaction as the one that matches a signature, and this is why it is a bad thing for lightning, as this essentially can mean the difference between a truthful record of the channel state changes and me robbing you
with schnorr signatures on the transactions you can't twiddle those bits on the edge, segwit is a countermeasure that only applies to ECDSA signature algorithm