[@_ck_ Participant 17 years, 8 months ago]

Unfortunately the search feature in bbPress is very poor. It can’t be (easily) modified like you are asking.

I’ve been working on a search replacement but it won’t be released for awhile:

http://img183.imageshack.us/img183/2061/sscy1.png

Note that you can see all posts by a user in their profile.