a post regarding that:
There isn't really any rule against it per se and it's not really enforced at an admin or staff level, so it's more of a community issue right now much like scams and other such shady behaviour. As far as I'm aware the only thing that is currently prohibited is merit sources selling their merit though I'm not sure what the punishment for that would be other than them being removed as merit source.
And this post is somehow relevant to this thread:
I think that tagging may be appropriate in particularly obvious cases, or particularly egregious cases involving hundreds of merit points and several posts. But generally you should start out by assuming good faith, and only change that opinion as the evidence really piles up. Tagging someone immediately after an instance of apparently-inexplicable meriting is too trigger-happy IMO. Even if it is a case of illegitimate merit, even hundreds of illegitimate merit points are not much of a problem IMO, so you have to ask whether it's worthwhile to possibly make a mistake by tagging someone who is merely suspicious.
These were fairly interesting reads. I get that if twi people know each other and are exchanging merit it's not as unacceptable if they know the person is going to be a good poster. If I had a friend who signed up here and has posted well for a few months and is making good quality post, I'd give them merit to rank up for their next rank and I believe that'd be fair.
Though a neutral trust rating (as I stated) might be helpful for a first offence (or some sort of note here).
The negative feedback idea from hilariousandco is just asuggestion. It would to me seem unrealistic unless it's over around 100 merits that get transferred between people here.
However, no one you have accused here has explicitly denied doing it so stick to what you're doing OP.