Even if it is not written in the forum rules, it is not allowed and that is why you want to give a negative feed back to the OP as you demanded if the forum does not kick against it. It is not everything that must be written down.
Then it's different, it's incorrect to say purchasing merit broke the forum rule.
Allowed or not, it's depend on the users. For me, I don't like it because that's a way to cheat, it's not fair for self made users that start from zero. Other people might disagree because they have their own perspective, they might put my name on their distrust list.
If it's written on forum rule, no one can argue.