What if, instead of having a cool down period, a users posting cost increase or decrease by certain x% amount which is determined by the success of the previous post?

The more successful the previous post, the less your next post cost. I think this would deter users from posting random stuff and it would encourage them to make sure what they post are valuable to the community.

You can have a scale: horrible (between 0-100 sats), good (101-500 sats), excellent (501 upwards). Depending on where the previous post ranks by the time a user post something new, the post fees will get a % increase or decrease according to that rank.