Code:
http://xenforo.com/community/threads/%D9%83%D9%8A%D9%81-%D9%8A%D9%85%D9%83%D9%86%D9%86%D8%A7-%D8%AF%D8%B9%D9%85-%D9%85%D9%86%D8%AA%D8%AF%D9%89-xenforo-%D8%9F.6343/
http://xenforo.com/community/threads/كيف-يمكننا-دعم-منتدى-xenforo-؟.6343/
Browsing with Firefox and Chrome it shows Arabic in the URL, but with Internet Explorer it shows the hex-encoded version.
Displaying Arabic and other languages in the URL is actually a feature (which IE apparently lacks) because %D9%83%D9 is what really gets sent with the request.
Edit: actually, when entering the Arabic URL directly into IE, the Arabic displayed in the URL.
Test one
Test two
Test one uses the hex encoded URL, test two uses the Arabic directly. They both work in IE, but test two shows the Arabic in the URL.
It seems IE just doesn't convert the hex on its own.
XenForo uses the hex version in the URL, likely to prevent unicode support errors.
Code:
<a href="threads/%D9%83%D9%8A%D9%81-%D9%8A%D9%85%D9%83%D9%86%D9%86%D8%A7-%D8%AF%D8%B9%D9%85-%D9%85%D9%86%D8%AA%D8%AF%D9%89-xenforo-%D8%9F.6343/"
title=""
class="PreviewTooltip"
data-previewUrl="threads/%D9%83%D9%8A%D9%81-%D9%8A%D9%85%D9%83%D9%86%D9%86%D8%A7-%D8%AF%D8%B9%D9%85-%D9%85%D9%86%D8%AA%D8%AF%D9%89-xenforo-%D8%9F.6343/preview">كيف يمكننا دعم منتدى xenforo ؟</a>
Accessing just "xenforo.com/community/threads/6343/" in IE brings the hex-encoded URL version from the redirect.
Clicking "next" may also cause the URL to revert, as it uses the hex version (untested.)
Tested with Internet Explorer 9 on Windows 7 64-bit.