I don't know how to tag on Gossip. I see a field called "@username" on the right, but I'm not brave enough to touch it.
Discussion
Ok, start typing a name into it. You'll get a little button below it like [@] which is a pulldown menu of the matches, if there are any (it is limited to people in memory atm IIRC). Select a match. You'll see it added to the p tags (listed under the draft) and it will insert a placeholder for you.
