I personally don't see a reason for this thread. Buyer was not satisfied with what he paid for, in this case due to corner issues, he sent them back and got a refund. You got your cards back in a condition that you still consider NM/MT. I would let it go and if I felt strongly enough that the buyer was wrong regarding his reason for return, block him and move on. But that is just my opinion and how I would have handled this situation.
Looking for - Jose Osuna, Clay Holmes, Alex Dickerson, Luis Heredia, Josh Bell, and Gerrit Cole