Unfortunately, the only way to delete all comments to your content forever is to completely delete the event being discussed. This means that if you don't like the discussion of your photo, you have to delete this photo. However, if someone's comments bother you, just blacklist this user and he/she will not be able to view or comment on your info anymore. And you can learn how to do this here. You can also delete all unwanted comments separately. Learn how to do this here.