There is a regression bug that prevents a UI warning from displaying when trying to create a user with a default email address (i.e. firstname.lastname@example.org). The UI warning displays in a clean 6.2.10 bundle, but not in Master.
The regression was caused by
Steps to reproduce:
1. Create a new user.
2. Enter in the basic required info, using 'email@example.com' or 'firstname.lastname@example.org' for the email address.
Two UI errors should appear, "Your request failed to complete" and "Please enter a valid email address".
Only the first UI error appears. "Please enter a valid email address" does not appear.