The "Registration Confirmation" / "Registration Confirmation and Receipt" fieldset and it's sections are displayed conditionally based on:
1. Is the selected Event a Paid Event?
2. Does the contact being registered have an email address?
3. Is "Record Payment" checked
If the contact being registered does not have a valid email address - the fieldset is displayed EMPTY (w/o any fields) when a paid event is selected (add or edit).
NOTE: Consider separating the fieldsets for "Send Receipt / Send Confirmation" from the the "Record Payment" fields - I think the fact that they are nested makes the form / tpl more complicated then it needs to be.
Please retest all the combinations after fixing this (3 x 3 = 9 combinations to test!).