As staff changes, there may be times in which a user must be removed. As seen in Section 2.2.1.3., a button in the "Modify User's Right" window provides just such an option.
Upon clicking "Delete User & Permissions", a confirmation dialog will display simply confirming the delete action. The two options will be "Confirm Delete" and "Cancel", both performing the options as expected. As the button mentioned, this action will both delete the User and all their rights from the backend databases.
As mentioned previously, a "Default" user exists to allow non-logged in actions to be performed. This user can never be deleted and the Delete User & Permissions button will disable whenever the user is selected by themselves or in a multi-select scenario.