Yeah, one thing Lemmy needs to solve is account migration. Instead of creating a new account on a new instance you move your existing account from one instance to another. It won't save the account if the instance is already removed, but it at least gives an option to move if you feel like there's a better instance for you.

Technically, anything can be scraped (e.g. Internet Archive), but that doesn't mean it's interactive.

I'd say the volatility of computer data means someone could theoretically nuke it whenever they want, though there may be remnants on other instances.

I'm curious enough to enforce Cunningham's Law: It's not on blockchain, so it's deleted if the instance is deleted.

Seems like the saving grace is anyone can either start or move to a different lemmy instance whenever. It's not like someone can just host their own copy of Reddit if spez ever went nuclear.