Why is all this necessary ?
How about the BMs just do their jobs, check the posts like they're supposed to and ban the spammers from their campaign ? They're pretty easy to spot.
I don't know how much they're paid but I'm sure it's enough for them to do that simple effort.
You see a guy posting useless stuff in megathreads, you remove him, you see someone saying "great project" or anything similar, you remove him etc...
Why create a rule that will lead to more cheating obviously ?
The bounty managers are paid anyway. Their payment doesn't depend on the quality of the posts of the participants.
If they are lazy enough, they won't care about the post quality...
If those who advertise with the signature campaign would differentiate the payment of the manager based on the post quality, that would be a motivation for the bounty manager to care about quality too.
But, unfortunately those who advertise with the bounty managers, also don't care about quality, just quantity....