TBH, I agree that focusing on the users would be a better idea. I have to admit that there are a couple of quality posters in YoBit/BitMixer; if the campaign itself was closed down because of the spammers, then that would mean that they would be affected as well.
I've banned, easily, hundreds at this point (can't give an exact number because some just received a normal ban). It's had very little, if any effect. At some point you have to accept it's not doing any good, and at some point you will cross a line where you are doing more harm than good. We spend a significant portion of time dealing with it, to the detriment of everything else.
Not sure if I understand what you mean. Are you saying that the signature itself would be automatically ignored for everyone, regardless of the user showing the signature? IMHO, ignoring a specific user instead of a signature type would be better; we would weed out the spammers, and the people who were making good posts with that signature would continue to get paid.
I like the idea of the ignore color; it sounded like a good idea. Maybe implement that again, but a less CPU-consuming method?
Yes, ignores that signature for all users if enough people have ignored it, maybe add highlighting to the ignore signature like the ignore user had.
Why not trial a simple limit based on activity/post ratio for anyone carrying a paid sig?
Whenever I see above about 6:1 and check them out, it's usually contentless repetition. It would certainly make people think twice before posting crap.
They'll use multiple accounts instead.