As the originator of our Blacklist, I remember when we as a team decided to add quality requirements to our control of the old free upvote system.
Just be sure to have some fairly clear rules, and still leave room for a 'at our discretion' too. With them paying, you can probably be a bit more loose than we were for the free upvote too.
RE: Brainstorming Subscription Sinks for SCOT Tokens & Tribes