my question is how that user wore the scam gambling site avatar in the first place or the banned restriction was for the signature only not include the avatar and they still can modify it to wear avatar, if so, they can still promote whatever they want even though they are ban wearing signature.
As you know, scams are not moderated on the forum and the signature ban has nothing to do with what the user has promoted so far. So, I don't think the main purpose of the signature ban is to not allow the user to promote a certain service.
The decision has likely been made to not allow the user to join signature campaigns.