Seems Mastodon has lists, but not a way to publish a message to just that list, ie "Send this activity to these 20 people".
Other than the fact it would require sending to each Actor and not using Shared Inbox, I can't think of any reason not to support this. Is there something I'm missing?
Oh I can think of a reason... because maybe the "bounce" part of that would then let a replier's actors see it. That's not hard to fix, but it requires some thinking about how to handle it.
emacsen.net is one server in the network