Delete comments on deleted defect?

Is there a way to delete or hide comments against a deleted defect? In our scenario, a defect was created and deleted but somehow users were able to make additional comments on the defect which has created a pin thread. Allow comment deletion is turned on in the server but I don't think it's viable to ask the users to go in order and delete their comments. I'd prefer to be able to clean this up as an admin and ideally permanently prevent future comments against deleted defects.