7/8/2011 1:07 PM
David,
Here's the logic: You can delete your own message as long as no one has already posted a reply. If a reply has been posted, then you only have the edit option.
I've tested it on these forums, and it's consistent with the documentation.
This should be why you're seeing it in some places but not others. When you have a chance, take a look at your postings and let us know if you're seeing anything different than this.
Thanks for asking the question!