A "participated threads" shortcut would be cool.

A more radical idea would be to go with a*"community builder" component. See a person's watch pics, "friends", etc. People are used to this facebook type of interaction now. Currently you get only to see a user's threads/posts, and that is done via an moderator's point of view. The inevitable "status update"&"wall post" might take a toll on the post count, but in the end, this is how communities evolved these past few years. Maybe it is for the best to follow..