Maybe, maybe not. Did you read those threads? At best, it was gross misrepresentation ("no fees at all", etc), and in the end the guy got banned after causing pages and pages of badmouthing due to his horrible PR efforts.
Like I said - abide by other forums' rules!
I think the best thing to do is to spend a little bit of time on the forums and find out who the respected posters are. Especially in the case of a girls-only posting site. Most often, those highly-respected posters will respond positively to rational and non-spammy inquiries, and they would probably be willing to look into it themselves and then promote it themselves.
You don't always win, since you can't always convince these strangers that what you're proposing is legitimate. But in this case just piquing their interest might be enough: a direct person-to-person, semi-anonymous payment system makes sense for girls with webcams. If it's a good match, at least one of the people you contact will look into it and decide to become the proponent for it.
It's a billion times better if a respected member of the community posts about it instead of a new member with one post. I'd almost rather that Bitcoin not get mentioned at all than see it cast into such a poor light by trolling evangelists.
Just make yourself available to those members to help them understand it and make sure they're saying things that are factual and correct, and use references instead of just telling them. In particular, I would reference the
Reuter's Article and the
WeUseCoins websites, mainly because Reuters is respected and shows that this is a real, respectable phenomenon, and not [necessarily] a scam. Weusecoins, probably gives a more-concise introduction to what it's about. Both are much better voices to promote its legitimacy than some shady dude with 1 post on a girl's only forum...