As for the topic at hand I believe, a change in feedback system/the trust system as we know it to include sig spammers would be more feasible and effective than banning one's signature. Correct me if I'm wrong.
As in what? Community members leaving opinions about other users (aside from a trust score)?
Staff given the ability to have a separate "trust" system, that should be a visible enough to let the campaign managers/runners know that they shouldn't accept the "person"/account. Or another system might be, an implementation of "DefaultIgnoreList" where if enough staff members think a participant shouldn't be running around with a signature, they can place them on the ignore list of everyone, with the option of members being able to manually remove them(which ofc only a few do even with DefaultTrust)