browser tooltip and MediaWiki div both warning invalid email
With $wgHtml5 now true on en-wiki, the form field attribute type=email in MediaWiki forms flows to the browser. This makes recent browsers validate e-mail addresses on submit. Which is fine, except when the form does its own client-side validation, in which case two validation messages appear simultaneously. See screenshot.
To reproduce, visit Special:ChangeEmail, enter a bad e-mail, tab out of the field, and click [Submit] or press the [Enter] key.
This may also happen with other forms using HTMl5 input types that trigger browser validation that do their own client-side validation.
A workaround is to disable the browser's validation with attributes novalidate and formnovalidate; it would be better to somehow cooperate with the browser's implementation.