Take a look up and to the right and you'll see that we've added a search bar to the forum!
The search results show the topic (AKA thread) that the search query was found in followed by a truncated version of the specific comment in which the search query can be found.
Unclick "Show Posts" and hit search again if you only want the main topics to display.
I hope this new feature makes your forum experience that much better. Enjoy!