How do you tag a user in a forum post?

[madscijr]

This may be a dumb question, but how do you "tag" a user in a forum post, outside of quoting them directly in a reply? In the past I found where someone tagged someone and clicked reply and copied the source for the "tag". I would expect in the editor something like typing @ followed by one or more letters would bring up a list of users, which you narrow down by typing more letters, and then clicking the user you want to tag. But that doesn't work here, and I don't see a toolbar button to tag a user, and I haven't found anything on the help page about it, so maybe I'm missing something. Is there a handy dandy way to tag a user in a post?