I wanted to send @kiamlaluno a note to say congratulations on being the first user to earn a gold badge. (Voting on 600 questions? That must have taken a lot of time!). But I don't see any way to send a direct message, and I don't think meta is an appropriate place for that sort of completely OT community cheerleading. Am I missing anything? Or maybe we could have a single topic on meta just for community chitchat, using @ tags so people see it?
This is not supported, and there are no plans to that I am aware of. (There are one or more MSO requests for this).
@ modifier only works in comments. Maintaining a topic on meta would not really be feasible, since a user must have participated in the actual commented item in some manner. It is also not an appropriate usage of meta.
You could just leave a comment on one of his many questions. Alternatively, there is the third place which is intended for chat.