What you can do is go through and request that each of your posts be deleted individually...sometimes I have to do that if one gets derailed and I end up talking about things I shouldn't and worry that someone might read what I have complained about and get whiny..so I ask to have just the post in question deleted...but if you ask for all your posts to be deleted individually then I don't see why they wouldn't effectively delete the fact that you were ever here..but for real the internet just stores info...so don't add what you don't want stored...