First, I'm sorry to see you go. I know that this probably doesn't mean zip coming from an Internet stranger, but meh.
So here's the thing... The OBS project is using a commercial software solution called Xenforo to power all this (= the forum). Unfortunately this software does not provide any functionality for users to delete their own account. As far as I'm aware this functionality is only provided through a (pair) 3rd party addon. And given the fact that OBS is basically a non-profit I can easily understand why they wouldn't go that far.
Anywhoo, I also feel very strongly about privacy concerns and while I don't agree with you on the subject... I'm going to try something (probably stupid?) in order to try and get some official attention on your request. Also given the fact that the privacy policy essentially points right back to these forums.