Honestly, at least a few of those threads should get locked up or merged into the social or whatever. You can go and look at character forums back and Brawl and Melee and you'll notice how the majority of the topics focus on the discussion of the character in their respective game. Even a decent amount of the Smash 4 character sub-forums are getting in shape for Western release.
Several pre-release speculative threads have been taken care of (locked up), and aside from socials, you'll notice that the majority of the rising and more active threads are focused on character discussion/development in Smash 4. Discussions on pictures, costumes, marketing, fan theories and other general statements are typically found in the social threads now.
Over time, users will actually include background information about the character in a guide. Though the guide's purpose is mainly to provide an overview of the character in Smash, there are plenty that open things up by providing some background info on the character just for others to appreciate them more. Still, we don't need to have a separate thread for those kind of things in every character forum, especially when there's other locations available to discuss general character stuff.
That's just how things are and I wouldn't count on it changing. It's not like you can't talk about that kind of stuff on Smashboards at all, so personally, I don't see much of a problem.