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This document is in utf-8, however it is served with;
which leads to it being interpreted as windows-1252.
The expected value would be:
Content-Type: text/plain; charset=utf-8
You probably want to add a directive like AddDefaultCharset utf-8
Note that this is not specific to text files, for example the HTML version itself is served without a charset as well (and it does include utf-8 characters), albeit browsers are able to pick it from the
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" />
header (I would recommend also adding the charset there, though).