I think this idea has been proposed and turned down already,
It has? Where?
It has been turned down here.
I don't think acting on campaign managers would work, they'll just stop posting here, or use anon accounts. While using anon accounts now would be a red flag for a sig campaign, it would eventually become normal and accepted, similar to how it's the norm to see a one post newbie selling a hero account.
That is interesting. While I could see sig campaign managers creating new accounts, I also don't think that many people who run signature campaigns want to see their accounts get banned. A lot of them are high ranking members, people who have posted decent post quality and are very active. Most of them have some amount of positive trust. I don't think that they would want to throw away their account to run a sig campagin. I have also seen that a lot of people running sig campaigns are the official account of that company here on Bitcointalk. I don't really think they would want to trash that account as well.
Besides, wouldn't those new anon accounts get banned for ban evasion?
As for signature campaigns without a manager, he's talking about bots counting the posts. Bit-X, BitMixer, YoBit, and a couple others do it.
Even with bots, there is still a person behind them. Someone has to run it, even if a bot is doing all of the work. It would be up to that person to deal with the spammers in their campaigns.