It's easy to slide by with haphazard (or no) moderation when you're small. Discussion extremists (trolls, bigots, and the like) are less attracted to smaller platforms; they'd prefer bigger ones, if any would take them.
I'm curious what will happen with the central listing of communities if a particularly vile community gains popularity. If there's a community unapologetically dedicated to, say, neo-nazism, and they like to do things like praise Hitler or discuss ways they can kill racial minorities, do they still get listed? How will others feel about that?