[usr1106]

I think the reality is that there are more speakers of bad English than native speakers. I speak 2 foreign languages (including English) daily and 2 others occasionally. I know I make mistakes in all of them. In English I don't think I make a lot of pronunciation mistakes (there are some mistakes in grammar for sure). In Finnish I make a lot of pronunciation mistakes, although I speak better than many other non-native speakers. How much that really hurts understanding I have no idea. The amount of misunderstandings between humans does not seem to vary greatly between those languages or even my mother tongue.

Text to speech should work correctly. But speech recognition should tolerate even clear mistakes. Of course not for the price of misunderstanding correct pronunciation.