I've never understood the universal acceptance of poor writing on mobile; everyone immediately throws their hands up and goes ahhh okay that makes sense then.
If only smartphones had some means of seeing the typed output... a screen perhaps? Icing on the cake would be some kind of backspace button, which together would enable proofreading! You know, like in other forms of written communication.
Basically everyone will insist it's entirely to be blamed on the phone, and we're expected to believe that no, really, the moment they sit at a physical keyboard they reliably distinguish your from you're etc.