My use case is that my usernames and email addresses match exactly - they have been imported from a previous system where users logged in with their email address and had no username. This works for almost all users, except where an email address contains the + character. In those cases my users are unable to edit their profiles because drupal throws a validation error on save:
The username contains an illegal character.I don't see any reason why the + character should be illegal. Can we please add it to the regex?
Patches for D7 and D8 provided.
