I ran in to a need for similar functionality 2 days after migrating our community. I have 3 or 4 moderators that are specialists in their fields, but for a lot of reasons, they may miss a conversation that I know they would like to (or should) participate in. While I can do an @ mention, it ends up breaking up the discourse with meta information which makes me sad .
".... greate point user x, and when we do y and z ..."
"I'm adding @ person to the discussion "
".... er okay, so back to what I was saying"
I would like high trust users to be able to do an action that performs the equivalent of the @ mention without munging the flow of the discussion. Alternatively, a way to mark the @ mention message as a moderator message that only high trust users see.