Sounds a bit like Plebbit, though that is more about P2P "communities/boards" that a user starts and others can post to, rather than a microblog type platform. Unfortunately it also has a strong association with Crypto communities as its founders come from that scene. It is built on IPFS.

What you describe also has similiarities to Secure Scuttlebutt and its successor PZP , which are both unfortunately abandoned but layed a lot of groundwork for asynchronous encryption key based networks.