It could be that paid signatures really have a hidden good. Ie prevent bs links to really bad shit.
Hmm. I hadn't considered that.
I would say the crappiest posters are outside sig campaigns and squirting their diarrhoea all over the alt sections with miles of links to Twitter or posting 'real' shitposts elsewhere in the hope of getting enough rank to get into a campaign.
I presume the forum operators aren't interested in experiments. They'd rather keep things humming while attempting to ease the junk to the margins. Perhaps a short sharp shock would achieve more but I can see why they wouldn't be into the idea.