So you mean if one is incapable of coming up with any decent content on his own, cannot trick others by disguising gibberish amongst long paragraphs, and cannot really be helpful in anyway, is he then allowed to gain merit as a trade for services, seeing that all other paths fail?

He can try, but there is no carte blanche to do it, so if caught (and there is a pretty good chance), there will likely be some red DT involved and it would render the involved accounts pretty useless from then on.