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Even plain text is no guarantee. This assumes that future people will read/understand/use latin characters. ASCII could very well be replaced in the medium-term future
I thought Unicode was already replacing ASCII.
What I meant to say, is that it's totally possible that, in the coming few centuries, even basic ASCII won't be readily understood. As in the character mapping in modern systems will break down, i.e., int 97 is no longer 'a', but some glyph from a language not yet conceived.
We take for granted backwards comparability. Just because ASCII has been readable for the past 60 or so years, doesn't mean it will continue to be for the next 60.