I think merit system is very good thinking by admin of bitcointalk.org. By merit system anybody can know his posting quality when another person give merit for his quality post.
But if anybody misuse this merit and sell it by money its fully opposite of forum rules and regulation and i think it should be punishment for that.
There's already a punishment as tagging the account of merit abusers. It's not easy to spot it however, if its blatantly obviously at some point, DT members will not be hesitant to give that account a red paint. However, I'm not really sure about the red trust is effective though, because if you go around bounties, there are still campaigns accepting participants even though they have a red trust.