They will definitely get credit for helping him.

Now we're discussing different case?
When he get so many merits in one day, it's because he posted in merit countdown to rank up, make sense.
In this case, he gets merit from his friends and unfortunately we can't do anything here just because giving red tag to merit abusers is inappropriate. In the past, people are meriting each other in their local board, now they're getting clever, they merit on global board in order to make them looks have a quality in global board.
Anyway if someone not agree with me, prove me wrong, if they're not from the same local.
