JellyFin
Booru-style Image Boards like rule34
ArchiveOfOurOwn
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For custom feeds, adding a weighting system to control how much of each source is shown is a brilliant idea. Sharing filter settings makes a lot of sense too.
For user trust levels, privileges could include post deletion/editing, banning users, pinning content, etc. Starting privileges low and slowly expanding them as reputation grows allows for decentralized moderation. The idea is Discourse or StackExchange moderation instead of Reddit like moderation.
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