Maybe a solution would be to make impossible to delete a merited post.
Since we are talking about deleted posts on this topic so in my opinion, preventing a post to be deleted when it's already awarded merit by someone - could be a possible solution. You do not need to remove the account. Excessive abused account should be banned when we will have solid evidence. The ban should not be just out of suspicious behaviour.
People should lose the merit if the post is deleted for whatever reason. Allowing it is just ripe for abuse as people can just merit shitposts or posts that are in fact copy and pasted then delete to hide the evidence.
I guess we already know that merit is not removable or reversible. There might be someone in a topic made a real good comment and awarded merit, later the mod thought the topic should be removed (for any reason) means that merit for the good post will also be deleted.