*sigh* I should have predicted that my simple comment would end up in this sort of discussion and worse yet would make me look foolish. ;-)
Let's just say that your point is valid and correct. It still does not make me look C-style "string" handling favorably. The few instances where you have to take a copy to detach a substring from a longer string, or to avoid quadratic performance of string concatenation loops are imho not materially significant compared to the benefits of making strings easy and nice to use.