notabug.io was favorite reddit-alike: https://github.com/notabugio/notabug . It was designed to be both server<->server federated and p2p to bridge content between unfederated servers. But like above, it was quickly over-run with genuine assholes which made using it distasteful and it eventually died. The technology was and is amazing.
notabug is a p2p link aggregator app that is:
distributed: peers backup/serve content
anonymous: but don't trust it to be
psuedo-anonymous: users can create optional cryptographic identities
immutable: edits are not supported for anonymous content
mutable: edits are supported for authenticated content
PoW-based: voting is slow/CPU heavy