[XeTeX] latin-1 encoded characters in commented out parts trigger log warnings

[jfbu]

Hi,

consider this

\documentclass{article}
\usepackage{xstring}
\begin{document}
\end{document}

and call it xexstring.tex

Then xelatex xexstring triggers 136 warnings of the type

Invalid UTF-8 byte or sequence at line 35 replaced by U+FFFD.

Looking at file

/usr/local/texlive/2020/texmf-dist/tex/generic/xstring/xstring.tex

I see that this matches with use of latin-1 encoded characters in comments.

Notice that it is a not a user decision here to use a latin-1
encoded file.

In fact I encountered this in a file I was given where
xstring package was loaded by another package.

Regards,

Jean-François