Conversation

ActivityPub/OStatus..
Actually, this reminds me XMPP.
An open protocol, a decentralized network, and people could communicate with each other no matter what instance.

The funny thing is that in their earlier days, Facebook Chat and Google Talk both were fully XMPP compatible.

But you know, walled garden principle. Embrace, harvest, split, dominate.

XMPP is obviously alive and well.