This is an annoying thread. It's annoying because the question of how to leave a group is just, well, unnecessary. Just don't come back. Go to your member info and delete it. Delete all your previous posts.
Secondly, if you feel the need to announce to the entire forum that you are leaving, why wouldn't you log in as yourself. What difference does it make to everyone that "unregistered" is leaving. No one knows who you are so no one can be prepared for not hearing from you anymore. A simpler thing would have been to privately message a moderator and tell them and ask them any questions you had.
Thirdly, as far as people knowing your personal information, that's all on each individual. This is the internet, everything you ever type, picture you post, anywhere is out there and accessible by anyone who may want to see it or have the knowledge on how to access it. I'm pretty sure the Moderators are trying to say that they just know who is posting as unregistered. As in that if I posted as unregistered they would know it was Daycaremum, that's it, not that they knew every little personal detail about me!!
People have to know that even in closed sites, people can copy and paste anything you've typed, take a screen shot, even take a photo of their computer screen!! What you type and post is out there, don't kid yourself that there are any truly "private" sites.
This whole thread is strange.