Scam accusation board is full of complaints to casino that has active signature campaign while most the user defending it are wearing casino signature campaign that gives a bias impression to the OP.
In these boards you mentioned, it's not only those that wears the signature of the accused campaign that defend the accusation laid against the project they are promoting. If the OP will feel biased of the judgment from members that are wearing the signature of the accused project, then the OP (accuser) should only read the comments or judgement of those members that are not wearing the signature of the product they accused.
Whether signature is disabled on those boards or not, any OP that creates a scam accusation thread can still see who is wearing the signature of the campaign he accused by just clicking the user's name and their profile will open up with their signature displayed on the profile.