If negative tags don't solve the problem of people continuing to promote this campaign, is it possible to expect a signature ban for each participant? Is this signature ban also a moderation of scam?
The rules of the forum should not be altered only because a certain scam gambling site is running a signature campaign and promoting scam.
But we can play our part by reporting the posts made by the spammers in that campaign. Since most of the posters in that campaign are not well known for their writing skills, their posts most likely will get deleted if reported by one or more members of the forum. Once the posts the deleted, the participants won't be paid and hence, people will be discouraged to join this campaign.