Hi Alex. The ability to do that was disabled a while ago. If there is something you wish to have deleted, you can edit it, or flag it or send a private message and I'll take care of it as soon as possible.
When someone replies to a topic and deletes that reply post, they will also delete any comments that were made to that reply post. Certain members would continually delete large numbers of their replies and take numerous comments with them. Trying to follow a topic after these replies and comments were deleted was leading to some confusion by both other members, the authors of the comments, and new readers of the topic.
As a stop-gap solution, the ability to delete topics has been disabled.
Mz Spelling Bee do you know why I am only getting one kind of crystal on my mountain? Then I go to the crystal grinder and can't get it to crush different crystals. I try to dig in different places but still just the pink one. Thanks ern