I mean they should earn at least X amount of merit per month, or they're kicked. Anybody who hasn't earned at least 1 merit since the start of the campaign, should also be kicked IMO.
What the purpose to add that as a rules? Are you mean merit is the way to prove someone is a good poster?
IMHO, you couldn't judge someone if he is good or bad poster just look from his merit history, because merit is subjective. You can earn it not only being a good poster, but making people laugh of your post (creating meme or have a good sense of joke). The best way to judge his post is check his post history... and I think the managers actually know it before.
Anybody who hasn't earned at least 1 merit since the start of the campaign, should also be kicked IMO.
A quick check from me, I don't find any single participants doesn't earn 1 merit since the start of the campaign. So, no one will get kicked.