This<br><br>
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<p style="margin: 0px; text-indent: 0px;"><a href="http://www.tug.org/pipermail/xetex/2008-July/010362.html">http://www.tug.org/pipermail/xetex/2008-July/010362.html</a></p><br>really needs to be documented explicitly in polyglossia.tex or fontspec.tex.<br>

It isn't obvious.<br><br>Also, it isn't nice, really.  Various language \hyphenation{}s belongs in the preamble, ideally.<br><br>Best,<br>Dominik<br><br>