Right now, you go to someone profile and you want to do a search for every topic that this user has started. You can't do that. The only thing that you can do a search on (by default) is all the post that the user has made.
Now you could get around this by going to forumname/search.php but it would be nice to be able to do this in one click from the user's profile.
Putting this feature in should be a no brainer as most of what is needed is already there. We could almost use all the same code that is used for the search post link and so on on the user's profile. As far as I can see, the only permission that may need to be created is can search user's topic.