I believe the reasoning is that you need some kind of moderation access. If every user had moderation access, then you could edit anyones post in the forum you are subscribed to. At that point mayhem would break out and the forum would be useless. The wheels that drive this forum (ih8mud) are huge and well maintained, just the spam filters alone are amazing. I mod this forum, but have no moderation access to any other forum, there are a few super-mods, but even they have restricted resources. Then you have the ih8mud god, Woody, who can do whatever he pleases, he owns these forums.
There is no need to delete posts unless there are personal attacks on someone, sometimes the information that you might not think is relevant may be useful to someone else. If the thread is indeed done, it will soon get buried under the hundreds of other threads above it, hard drive space is cheap.
If you want to change the title of a thread (in this forum) ask me. Otherwise you will have to ask the mods in each forum for a change. Some of the mods won't even acknowledge such requests.
Just because you started a thread doesn't make it yours, once posted on a public forum it becomes public domain. Having said that, if you have a thread you want deleted I may be able to accommodate.