Confusing CiviMail unsubscription confirmation screen
Most of the code for the actual unsubscribe process is located here:

CRM/Mailing/Form/Unsubscribe.php

Would be good to:

a. Create a site wide CiviMail setting so an admin can disable the email confirmation process.

b. Use this site wide setting to determine the behavior of the code, the new behavior or the 4.4 and prior behavior. The 4.4 code is here:

CRM/Mailing/Page/Unsubscribe.php