So late last night a patch got merged in core which had the knock on
effect of creating a bad experience on mobile. The change basically
notified a user if their username was adjusted e.g. uppercased or
spaces removed. Since most mobile device input fields default to
lowercase rather than Titlecase, this means that pretty much anyone
who now tries to register an account on mobile will see a warning that
their username has been capitalized and will have to fill in the
registration form again (yikes!)

I reverted the offending change for the time being
https://gerrit.wikimedia.org/r/#/c/117234/
but according to Greg the branch has been cut and it will now need to
be backported.

It would be good if we can get this lightning deployed so that this
doesn't effect account creation numbers on mobile.

Anyone able to help out here?