Unfortunately, I think all of the other forums I visit outlaw personal promotion or advertisement for personal gain of any kind in the forum signature. So, I don't think I would be abiding by forum rules by asking for Bitcoin tips in any of them. But I did, for now, at least link to a daily bitcoin chart. It'll give people something to look at and pique their interest.
That's strange. This is not common in Finnish forums, none that I use have this policy. Well some don't allow signatures and avatars in general but that is different, those boards are probably just running museum software.
I think it's a good idea to promote Bitcoin this way. I'm basically promoting my own site very blatantly everywhere but the site is (or will be) only semi-commercial. It's a Finnish Bitcoin information/news portal primarily so I don't see it as a problem, I lead people there to learn about Bitcoin, if I get something out of it later then good for me.