international chars in form

[eluser]toltmanns[/eluser]
I've dug a little deeper and have found the function clean_string in the system/core/Utf8.php is causing the issue.

$str = @iconv('UTF-8', 'UTF-8//IGNORE', $str);


http://www.utf8-chartable.de/ shows that the enyay (below) is in the charset
U+00F1 ñ c3 b1 LATIN SMALL LETTER N WITH TILDE

So I am wondering what if the function clean_string is working right, php.net says that the first two arguments are in and out strings, so why does the system assume that I am inputting UTF-8? Why, if the character is included in UTF-8, is the function failing?