There's also Aether, which has a system based on delegation:
https://getaether.net/docs/faq/voting_and_elections/
In essence, you can either curate all content yourself, or you can upvote other people's curation for a given community. The curators who are voted for by the majority of a community effectively become the default moderators for it, but any member can explicitly opt out of curation by any given moderator.
With the new Freenet, we're using a decentralized moderation system that lets users control what they see or don't see, based on sensible defaults. This builds on a concept from the original Freenet called web-of-trust[1]. I believe this method, combined with the fact that centralized censorship is impossible in the new Freenet due to its lack of centralized control, offers a strong alternative.
[1] https://github.com/hyphanet/plugin-WebOfTrust/blob/master/de...