(a) Markup to the body, that has the purpose to indicate that a part of the body is referring to a user or a group of users (b) Some indication that the message should have some sort of priority to a user or a group of users
In the direct mention case, I don't think we really wrnt to allow one without the other. I am also against noping though. It is not up to the sender if I want to be notified. And if we use occupant id the idea of cross-room mentions becomes not possible. I'm not sure what the use case for those is but if we wand that I suppose we should use URI. At which point we are maybe back to a minor update the references XEP rather than a nnw XEP for this, per jdev discussion the other day. Just need a URI for occupant IDs which we could define new or GC3 style (xmpp:muc/occupantid)