From what I understand due to the way that Lemmy handles federation, it doesn’t (currently?) have a way to handle an instance changing its domain name and still being able to communicate or even an individual user changing their instance and retaining their comments/votes/etc… (this might be more ActivityPub limited since the way Mastodon does it still seems pretty hacky and just a work around for underlying issues).
From a website perspective, yeah, just change some settings and you’re good to go and accessible on the web, but that doesn’t mean that anything regarding Lemmy is going to actually work.
From what I’ve seen: Linus didn’t ever typically rip into first time contributors, it was usually always the people that he either expected better of or people that just kept submitting crap after crap.
Still sucks to be on the receiving end of it though.