According to this page (https://help.salesforce.com/HTViewHelpDoc?id=user_fields.htm&language=en_US), "Unlike other hierarchy fields, you can inactivate users referenced in the Manager field." but what I'm trying to do is different, I think.
2 answers
I think you would need to activate the manager user, set them as the persons manager, and then deactivate them again. You're right though, not best practice.
