[Coda]

They won't ever use phone numbers for that -- that would be incredibly risky from a legal perspective due to COPPA and the fact that the game targets children. Not to mention that not every device that can play Pokemon Go is an active cell phone -- my son plays on a phone without a SIM card using wifi tethering to my own phone, and I've got a tablet that I COULD (if I wanted to) activate a data plan for and install Pokemon Go on and it wouldn't be able to make phone calls.

It's almost certainly going to use your display name, because that's separate from your login credentials.