We added the "How do I edit or delete my post?" section on November 26, 2007. (The Wiki history feature told me that!)
Using the Report Post feature is almost always preferable to sending a Private Message to a moderator. Post reports go to whichever moderators are available. If you send a PM to one moderator in particular, they may not happen to be around or may not be available to help you just then. The exception is if you are sending a followup about a previous conversation with that moderator, but that's unlikely to be the case if you simply want a post removed.
Use the Contact Form if you want to bring up an issue with the administrators and require a reply.