I believe most will agree with me that there is a high probability factor that people give merit to those who merited them in the past, therefore creating a merit ring. You can easily discover such people from their merit summary. This could simply be a coincidence or I'm just imagining things. But if this is true, then such individuals are cheating the system and us unfair to others who take time to put in the work to develop good discussions and topics.
Merit data is public so you can go ahead and prove it instead of speculating. However: merits are not scarce and the way the system is set up each individual merit sender is supposed to exercise their subjective judgement as to what is a good post, which given hundreds if not thousands diverse merit senders makes it extremely unlikely that "good discussions and topics" would get cheated out of merits. If you do have such examples you can bring them up in the
merit sorcery thread or directly to theymos so that he could appoint more merit sources in certain areas.
I wouldn't hold my breath that some complicated rules would be established as to who can send merits to whom and for what.