recipient that (a) is present for (b) to work, no matter if it's the same element conveying it or a different one.
I suppose that's true. The main thing is the problematic <message> <body>Some troll statement</body> <mention occupantid="blah" /> <mention occupantid="blah2" /> <mention occupantid="blah3" /> </message> Where these users get notified but don't know why. This was an early complaint when I implemented https://xmpp.org/extensions/xep-0224.html which I solved by highlighting the message as "this one is to everyone" in the UI. But when it's not to everyone, and indeed if 99% of the time there will be your name in the message, it makes more sense to highlight a name then to add some other UI. At which point you have a dependency on whatever does (a) anyway and they might as well be together if you need them both...