I am not if this is sure, but this is why big boards do not delete accounts, I have heard
them mention that it can cause havoc, also, lets say you have a member that has 5k
posts, do you really want to let those posts slip out the door? once a user
is deleted, then so will all the posts that the member created along the way....
ah, now i read the end of your sentence, delete member, but not the posts.
I think it would just be just as easy to ban the user instead...