There is a little black triangle in the lower left corner of each post. Click it and report the thread.
As for why you can't do it yourself, picture a topic with several interesting replies. Now, wouldn't you feel silly if the post you had replied to disappeared? People would think you were nuts.
__________________
Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.