I think only fixed rate campaigns should allowed, pay per post campaigns makes more spam on forum.Everyone in rush to make posts because they get paid more when they post more but fixed campaigns will reduce spam on forum and users will make posts only that is good.
So what prevents me from creating 10 accounts and using each of them to make 20 posts per week instead of 200 posts with 1 account? Nothing. Let's move on; this idea won't work. This especially has no effect on the quality.
What's preventing people from doing this already?
Fixed rate campaigns coupled with posts per week could be a good way to deter people from spamming while pushing them to include themselves in conversation.
Weekly pay,
BTC0.00x/week, min 5 posts of good quality and constructive commenting. Make sure the language of the poster is fluent in the forums where which they post.
People would be less likely to spam all over the place, while viewers and advertisers would be sharing quality paid content.