Finally someone sharing my views on XMPP. I can’t believe how many apologists XMPP has given how terrible it is as a protocol.
Hahah, that is probably the one lesson that ActivityPub has NOT learned from XMPP.
ActivityPub can support new vocabulary through an extension mechanism based on JSON-LD, and I honestly am curious to see where serious efforts in this direction will take us. So far only the group interested in code forges were doing any extension work, but I haven't tracked them closely.
Hopefully we've learnt that a) "everything is an extension" is a terrible way to design a protocol b) a protocol can be bad enough to destroy everything built on it.