Please take a look at http://bugzilla.xfree86.org/show_bug.cgi?id=544
and http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=296719.
Since there are a lot of free almost-full supported ISO10646 fonts in Linux,
like unifont, xfonts-efont-unicode and xfonts-wqy.
So I think that all of XLC_LOCALE for UTF-8 should be prior to use ISO-10646
earlier than ISO8859-1.
(AFAIK, at least ja_JP.UTF-8 and zh_TW.UTF-8 are broken.)
Please consider to recover it. Thanks.
This bug had been report at https://bugs.freedesktop.org/show_bug.cgi?id=8762.