First, there isn't any known rule or law guiding how merit should be used or sent around the forum, there isn't any rule forbidding or stating that two or more parties can not merit themselves if their posts are worthy of it, so personally, I see nothing wrong as long as their post are worthy of the merit(s) they received.
But if merit is abused, it should be posted about here so others can see it too. This forum does not against sending merit to any post, but if merit is abused, there is nothing bad to give such accounts that abused the merit to be given red trust. Seeing someone like that, nothing bad to bring it up here for discussion to know if other members will accept it true or not.