URLs contains non ANSII characters like(http://ar.wikipedia.org/wiki/الصفحة_الرئيسية) are rejected if it is put in bbcode like url or img and not recognize as URLs if it written in he post with out bbcode
The bug is in get_preg_expression function in functions.php file witch accepted only [a-z0-9] characters, so other utf8 characters are rejected.
get_preg_expression must contains the rejected characters not accepted characters like [^ ,.:] and other punctuation characters. To contain all UTF8 characters with as human read able.