Comment by jibal

This is correct, both about what happens and about what your P is not understanding. Your P's claim that "UTF-8 has no 8-bit restrictions" is nonsense. It's too bad that your GP wasn't clearer about what the problem is: not all byte strings are valid UTF-8. This is why people have had to invent hacks like WTF-8 (https://news.ycombinator.com/item?id=9611710)