Nothing really. The problem will mostly solve itself because it's a stupid solution to the problem of "ranking up".

First off, it's freaking expensive; 15$ per merit? I don't see many bounty hunters spending 150$ just to become Jr member/Member.
especially not when the chances of getting caught when buying merits is pretty damn high, maybe not if you buy a single merit, but when a shitposter gets 1 merit for 3-15 consecutive days for posts which simply don't make any sense, it really becomes painfully obvious, and your account will be tagged in no-time.


Also, each merit given has to come from somewhere. With the airdropped merits become less and less every day, this "merit" selling thing from account farmers will naturally become scarcer and scarcer to observe.