About open registration: we had a debate about that too, but actually decided closed registration didn't make that much sense because anyone can just go register on another instance and participate in our communities, so what was the point of gatekeeping registrations?

And ultimately that's a very broad problem with the fediverse. Yes, you can curate your own local community all you want, but if you accept content and comments from the other parts of the fediverse, it's actually a bigger moderation problem than something centralized. And there's a liability problem: even if you police your own communities well, someone could subscribe to something unsavory across the web and you're technically "hosting" it.

Federation isn't easy to get right. Ultimately it makes moderation less scalable, not more, because every little instance has to moderate the whole fediverse.