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?