Can't disable underlining

[SenderaGypsy]

I was logging in to a mobile account and my username has an underscore. When I went back to abc screen to finish login, letters are all underlined. It's not the app because I checked it just typing a text. Now I can't log in anywhere! What the heck?

 

[B. Diddy]

Welcome to Android Central! Go to Settings>Accessibility​, and see if any of those options are turned on.