I think your tone is a bit condescending towards people who have names that don't fit our norms, but to some extent I agree with you. Let's be honest, for every person with five hundred characters in their real name there's going to be a thousand people who accidentally pasted a bunch of text into the wrong field, and at least ten jackasses who are just trying to see if they can break your app in some interesting way.

Accommodating everybody is a pretty tall order (see: Prince). Where's the appropriate place to draw the line?