Yes, using the Report button is useful. Specially useful when it comes to merge threads since most of times those merges are not so evident from reading the subject only.

fyi what I'm doing from time to time is watching the N900 forum (mostly) scanning threads with more than 10 posts to see if they are in the right forum. Posts with <10 are only moved when they happen to be in the way and they are clearly out of place.