Another option would be the removal of merit which will go back to the sender. But it's much harder to implement I guess. I agree that merit abuse went too far on this forum.
This would be better, but the merit should just be burned and not sent back.
I agree with hillariousandco's suggestion, but there must be some slightest adjustment to make it better because the post deletion can be done by the user or moderator. I suggest the only thing that makes the merits disappear is from the post deletion by the moderators or administrators, because sometimes even a good thread that is filled with merits can be deleted for some legit reasons.
This could be true. But, deleting a good thread which is filled with merits would be one out of the thousand cases, and all the remaining 999 case would mean deleting merits transferred because of abuse.
You can also experience post count decrease and sometimes activity decrease because of the thread/post deletions. Only spammers care about the post count and the activity point, others don't really count their posts on a daily basis... Some time will pass and this will be the case with merits as well, only merit abusers will care about their merit count, other will just look at it once per week/month/year etc...