You can delete or deactivate ACS user records. Deleting a record removes the record from ACS completely, but if there's a chance you may need to update or use the record again in the future, you can deactivate it.
If you delete an ACS user, then add the user back, you can access that user's saved searches and reports. This is helpful if a staff member leaves the church or organization and you need to access these. However, all user settings in grids and windows are lost when you delete a user.