There is loophole way to edit in the User Panel even when you have Edit disabled in the event.
If you have edit disabled, the edit icon doesn't show in the user panel, as it shouldn't. but when you make a partial payment in the User Panel by clicking "Pay Now", the payment page it takes you to has a Back button on it. That back button will take you to the full edit for that registration for that event. You can edit everything as if it is enabled. This is a problem when you want to keep people from editing registrations. Someone can stumble onto this and change it all.