If i remember correctly, the merits system was made to improve post quality (and things that help the community, i've seen that people give merits to do infographics about the merits system). Yes, they've good designs but thedtre was another way to appreciate the help they were receiven, as i said before, by the Trust System. Are you trying to say that if they aren't merits souces, they can do merits exchanges?
Merit sources are not allowed to sell merits. That is the only rules as far as giving merits is concerned.
If there are blatant examples of misuse of merits (this is not one of them), then default trust members may give out negative trust. Theymos has said that DT members should not be trigger happy and jump to conclusions in these cases.