[support] Remove user: do not delete user

Hi all. When a user want to delete from my site , for an italian privacy law (in words more and more simple), I can not delete him/her data from my DB but I can only delete his personal data (rewrite it with REMOVED is enough), but not the email because the police can ask me who write a comment or a node for some month after him/her delete him/her account. (The italian policy law is more and more "articulate").

I know that there is a hook_user() but how can I stop Drupal from deleting my user ? And I don't want the drupal change the uid associated to the nodes that the users has write, too.

Tnx for all.