@OP, if you are convinced that they are legit and deserve to be promoted and you are not going to spam the forum or post extra posts just to get few bucks then you can join their signature campaign. It is easy as that.
I tend to agree with what you wrote. There's nothing wrong with being in a sig campaign if you're a good poster--unfortunately the Yobit campaign has historically recruited the dregs of the forum (with some exceptions, of course).
I would also argue that it's not only important that the participant be comfortable promoting Yobit, but also that the community doesn't think they're a scam exchange. The risk is that the campaigner might get tagged for being in the campaign. There was a lot of discussion about that the last time around. Personally, I don't think they're truly scammers. They just have abysmal customer service and awful business practices to boot. But they do provide a useful service to a lot of people, and I know there are many satisfied customers--me among them, because I've used them a lot in the past for small trades.
I have just joined the campaign again and this is my first post wearing the cryptotalk signature; i will watch if it will be counted before continue posting.
Good luck, and I would advise you to make above-average quality posts. Last time a bunch of members got temp banned if they had reports made against them which were marked as good. You don't want to chance that happening again.