As parent said, XMPP covers all of these cases with plugins. The FAQ you link says, over and over again, "the base setup doesn't cover these features, but plugins do," and doesn't explain away writing improved plugins or XMPP spec extensions. All I see is "buttt it'ss haaaaarrdddd".
> Rather than fighting over which open interoperable communication standard works the best, we should just collaborate and bridge everything together.
Absolutely dripping with irony.