That does not make sense to me. on Page 19 of the Using Pega Robotics Desktop management Console document, it states: "For reporting purposes you cannot delete users, you can only deactivate a user. To handle users who leave your organization permanently, create a department called, for instance,Sacked, and drag and drop those users into that department."
If Deployment Portal were to actually delete users, this could distort the information you see on reports. Instead, you simply deactivate the user and set up a department for deactivated users. Then move the deactivated users into the department you created. The name you assign to the department can be anything you choose.