It's something I don't like about what programmers tend to mean when they say plain text: Plain text isn't the same as ASCII. It isn't the same as Latin-1 or some other eight-bit encoding. UTF-8 is plain text. UTF-16 is plain text, too, but UTF-8 is better to use on the Internet.

My point is that you can go well beyond the Latin alphabet and still be in the world of plain text. You can have correct quotes, as opposed to the apostrophe-quotes typewriters saddled us with, and still be producing plain text. There's nothing inherently "fancy" about using the writing systems most of the people on Earth are fluent in, and, thanks to Unicode, there's many fewer compatibility problems.