I had written a mostly functional system based around exchanging gpg-signed anonymous messages, usenet style a few years ago, with distributed voting, opt-in moderation, and server federation.

https://github.com/e1ven/tavern

I eventually moved on because I couldn't figure out how to solve some of the social problems, but I still think something like that could work out.

Do you have a document (or a set of issues) describing the social problems you were trying to solve? They may have already been solved, in some other context.