uniq weirdness

Bug or feature? Maybe just a misconfiguration locale, no idea, haven't looked into it, anyway doing this:

uniq << EOF
：
？
！
（
）
EOF

Produces this:

：

All the other characters are missing. If anybody is wondering those about those character, they are fixed size versions of your regular :?!() characters and are used in Chinese.

Edit: sort -u seems to suffer from the same issue.