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.
I don't know how much account creation timers would matter. I saw one troll account recently whose account score did not match his eight or so comments, so I think it was an abandoned account that got hijacked. Either that, or this guy has been planning this out at least a year in advance, which is psychotic enough to justify permanent institutionalization.
I mean, even if the guy made full anime villain preparations he would run out of old accounts pretty quickly. Freezing signups is a blunt tool, but it works.
If the regular users report the pedo comments, and the mod(s) are active enough, it doesn't matter how well the trolls prepare. They'll get their account nuked, and be forced to make a new one. We dealt with that troll on ConsumeProduct for months, and he still occasionally makes a new account to push his degeneracy. However, the users there are quick to report him, so the mods quickly ban him.