About the foreign community stuff:
Since most members of these fanbases are still kids(in their behavior), there will always be these kind of experience. It's all because of this childish prejudices, but there is nearly no way to prevent them except thinking.
But there are also many people who want to share the game with other people, and some, for example me, find nearly no fora or whatever else in their mother language, so they try looking for some in "more popular" languages(with success, as you see).
I bet there are many Japanese fans who would want to work with an english community, but it's not always possible.
As for the topic, why just working in one part? I mean the people skilled with TF can make more TF Tutorials(maybe easier ones), and some may take the fanstuff section or whatever.
Giving people a bigger range of possibilities makes them want to be part of the community, but even without this range, who doesn't want to be?