I'm not aiming for precision with this answer, but RetroShare[1] comes to mind.
What is RetroShare? It's a communications and file sharing software (and protocol) similar to DC++, Bittorrent with peering based on public key cryptography. On top of the network and security stack, services such as IRC and MSN-like messaging is available. A message board for sharing posts and subscribing to "channels" used a rating system by votes (IIRC).
Today I'd describe it as similar to Keybase or Matrix, but peer to peer, instead of federated or centralised. It was much a developer-and cypherpunk-community.
Several years ago I spent a lot of time in the network because the social aspects were interesting. Reputation management went deep. Not accepting someone's public key (blocking) would render their data useless so you don't had to engage with it.
This got longer than I expected, but I felt nostalgic.
[1]: https://retroshare.cc/