Simply put, would be nice to one click to a user's other non-closed threads in the marketplace.
Makes shopping/selling easier to manage I'd say.
On that note, a simple button next to the pm/profile button to search a user's posts is welcome as well; see geekhack.
^A.t.m. you have to login to be able to search quickly, going from a post to someone's profile to his/her posts; or directly search, username. On GH it's: see a post, click username, click show posts; without login.