Could this module share code with field_validation (itself borrowing from webform_validation) so that the same extended set of validation criteria could be applied to usernames? I am not marking this as Feature Request as I don't know whether it makes sense or not...
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Comment #1
lolandese commentedDevelopment status: Maintenance fixes only
Furthermore it would make more sense to do the opposite, extending https://www.drupal.org/project/field_validation with support for usernames.