Hi Roberto,
I believe its deliberate. You can however set the user status to delete IIRC. This is due to the fact that a lot of objects ties into the user object. For example what happens to my post in case you decide to delete me?
I was successful though in deleting users, in my case I was sure the the users and its referencing data are to be deleted too. So I deleted the posts, files, etc. and finally the user. I was happy to say due to OACS data model it was easy enough to query the db to delete the related objects. Imagine if it was a mySQL based framework, oh yeah on such a framework they do not care data integrity. They will just outright delete the user and leave the other related objects scattered.
BTW, CCM for some weird reason remove the user status (ban, delete, approve, etc.) :(
I hope you are not looking into this because you want to delete a user in openacs.org :)
