Hrqls: there are some people who dont read this board as they are only interested in the games and not in the site itself ... those people might miss the discussion about the specific game

That, IMO, isn't a good enough reason. If people don't want to read board X, than that's their loss if there are a few posts on board X that they might be interested in. Hey, I don't read the music board, but that doesn't mean I'd like a thread to be continued on a board I do read if it's about a subject I might be interested in.

There will also be people who are interested in starting colour effects that do not read the Knight Fight board, and you'd hurt those people.

And, finally, one should spread threads out over boards too lightly. It becomes harder to follow a thread - specially if people search for it. One board will have a thread without an end - the other a thread without a beginning. A lose-lose situation. Considering there were only a few posts about Knight Fight in the general discussion about starting colour, I'd say keep the discussion together. If you don't want to read it, just scroll up.