I agree. I don't think all signatures should be banned, but maybe make paying per post not allowed instead.
There is no sure way of enforcing that.
So, instead of enforcing a detail like that, we should enforce based on the results. Consider the no giveaway policy we made in the Altcoin board: We don't actually say that giveaways aren't allowed, but rather that incentivizing low-value posts isn't allowed. When people tried to get around the rule by doing things like "IPOs", they were still dealt with because of how the underlying policy was worded.
I would argue that the
same exact policy should be applied to sig advertisers. As long as an advertiser puts in a good-faith effort to prevent low-value posts and is willing to disavow people who make low-value posts anyway, they would have nothing to worry about. If they
don't put in a good-faith effort to prevent low-value posts, their site gets added to our spam filter.
If we can get some consensus on this, we can see if theymos would be willing to do that.