@clacke thanks! I'm not sure there's written material on it, but the intention of MIMI is to learn from prior attempts at an interoperable protocol to build something which actually works. XMPP has largely not been adopted in this sphere, though is popular in its own right. Matrix has additional features that don't translate well to other providers as well (we'll talk about this in the talk).
It definitely feels a bit like XKCD 927, but this time we're going to interoperate with all of them :)