No change email address for / delete identity on extensions.gnome.org
When logged in to extensions.gnome.org, the User Profile page allows only the username display name to be changed and the User Settings page only provides the option to change the password. There appears to be no way to change the email address (or username).
There appears to be no way to delete an identity once created.
The How to Access, Modify or Update Your Information section of the Privacy Policy for the GNOME Foundation says,
The Foundation gives you the ability to access, modify or update your personal data at any time. On sites where you can create accounts, you may log in and make changes to your login information (change your password), your contact information, your general preferences and your personalization settings. If necessary, you may also contact us and describe the changes you want to be made to the personal data you have previously provided by emailing info@gnome.org.