I bet you could do it with ring signatures
a message signed with a ring signature is endorsed by someone in a particular set of people. One of the security properties of a ring signature is that it should be computationally infeasible to determine which of the set’s members’ keys was used to produce the signature
I upvoted because I’m generally excited by the idea of software that lets you interact with different social media via one interface. Idk if the project itself is good but it seems like a neat idea.