I think it's an inherently hard problem. The one I fear the most is not the toxic dirtbag; they just get banned. I'm more afraid of those who follow the rules but reliably kill the vibe. The internet has no equivalent to the whole room going quiet.

It's a lot harder to moderate bad actors if they can keep creating new accounts, too.

Agree, it is hard. I've built a few communities, and trust my gut; if something feels off about the vibe from someone, it probably is and I should be wary. But this becomes incredibly difficult (if not impossible) to put into rules, so if you're trying to build a community where you're not the beneficent dictator for life and there are published rules then you kinda have to accept that some people will play the rules and be dicks anyway.