When you fly downwards your name tag turns invisible as if you were crouching. I know they removed crouching when going downwards but it appears your name still turns invisible. Is invisibility just bind to the shift key maybe? The key that crouch uses as well as fly?

Go into creative mode on multiplayer and have a second player go behind a wall. When then fly down their name will turn invisible as if they were crouching. When they are infront of you you can also see their name tag turns "darker" or invisible as if they were crouching.