There is a little problem in merit system which it is the deleted post , For example :
When someone gets merit point from another user, he can delete their post ( especially when their post does not deserve a merit point ) and the problem that the other members cannot read this post anymore and when someone else clicks on the link of this post (on the coordinate of Merit) , it will appear " An Error Has Occurred! "
Maybe the best solution will be : The post who gets a merit point their owner cannot delete it .
Hopefully that theymos will correct this problem.
It's not really a bug.
The system records the URL that you gave merit to. If that URL is deleted, obviously it will throw an error.
Theymos has stated deleted posts will not reduce merit.