selling or buying merit is not against the rules,there will always be people who try to abuse ANY system in place
the thing is,they cannot just get away with it easily
if their posts are rubbish and they get 5-50 merits for an obviously spam post (or a "special" merit magnet topics as I call them)
the rules also do not prohibit for a D1-D2 trust member to waste their efforts by red tagging
don't know where the 28$ figure is coming from,but that is crazy