Occasionally users sign up using their email address as their username.
The default behaviour is for users to be identified to other users by their username but when they view their own content, they see their full name.
Problem: these users don't realize their email addresses are being published openly on the internet because when they look at their content, they just see their full name. I have a feeling that if people realized their email address was being published openly, that they would be unhappy.
Users can resolve this by granting access to their full name, causing it to be published in place of their username, but their email address (username) would still be exposed in certain links and in source code, so the only real solution is to not use email addresses as username.
It might be better if users were always identified by their usernames. If they have granted access to their full name, that could be published alongside.