We need to nominate a dude to the mod team for the EXPRESS purpose of banning this weirdo's alts. I'm grateful to u/DomitiusofMassilia for popping in every few days, but sadly that's not frequent enough. We need a daily reader who can just hit "ban" when he's browsing comments. It won't solve the problem but it'll alleviate it.
We could also freeze new account creation and open it for select periods, announced with pinned posts. Our growth would be disrupted of course, but it's not like that matters that much.
That's far from the ask. He's super obvious, you don't need to stalk him, just hit him when he pops up. Anyone who's trustworthy and spends a lot of time here could do the job with very little effort; when you see more of the posts/accounts, ban. Easy.