I've noticed something odd about Facebook comments.
Let's say you have a friend, post a comment on their wall or reply to a comment they have made. You can see this comment in your activity log to view and delete.
However, if you unfriend this person, the comment disappears from your activity log. So you are unable to review or delete?
If you add the person back, the comment reappears in the activity log and you can delete.
Is there a solution to this? Apart from adding back the person? Since again, you don't have a log of who you add / remove.