actually, thats sort of what we have here, just becomes a matter of making mention sends immediate, mention receives immediate and polling private. Also need to auto-tag the reply-to, which i think would be the most complex as if you start replying to posts out of order that could get messy. Also, how do you group message?

my generation deserves better chat clients than Hangouts and iMessage
Not looking for ideal, I just want the experience of AIM circa 2001 back… :/
Indieweb Instant Messenger! Let’s make it happen. :]
Tell you what though; I’m kind of thinking private posts and webmentions behind site-to-site oauth is a dead end. So many points of (invisible) ...
I agree it feels pretty heavy for what it is doing, perhaps for this protocol it would have some authenticated version of webmention that would ...