Soon both accounts will be banned or at least will get negative trust.
This isn't an offense worthy of ban (they haven't broken any forum rules which consequences is getting banned), we're also discourage from leaving negative feedbacks on users account for behaviors that doesn't involve trust like spamming, merit abuse etc best solution would be a reversal of the transaction by theymos.
No one will be banned simply because of shady behaviours with trading or merit transactions.
Yes, both of you are right. No one will be banned for merit abusing. Also, I agree that reversal of such a merit transaction is a good idea.
But as far as I know admins (or maybe only theymos, I am not sure) can ban suspicious accounts until they prove their ownership. I have seen some topics about such cases in "Meta".
The account that has sent those 50 merits might have been hacked.