Looks like a classic case of merit sales to me.
• User A has lots of farmed accounts and advertised merits for sale on telegram, discord or wherever else they do,
• When they get a buyer, they pick one of their accounts to send the merit through,
• They know this would have a negative impact on the receiver, but do not care much for that.
It would be a bad way to run a business if he sent 3-5 merits every 10 days. Most likely no one would notice that, but suddenly appear with 50 Merits, I do not think it is a behavior for selling merits, especially if seller is active on the forum.
It is not the first time and it certainly will not be the last, so you should not use merits as trust feedbacks.