It seems that hyperlinks containing non ASCII characters do not show up. Examples: [url]http://ja.wikipedia.org/wiki/文字コード[/url]; [url]http://ko.wikipedia.org/wiki/문자_인코딩[/url]; [url]http://pt.wikipedia.org/wiki/Codificação_de_caracteres[/url]

Any way to fix this?

I don't know a way to fix that, but maybe you can use Firefox to copy the URL, as it will use Hex instead of Unicode.

http://pt.wikipedia.org/wiki/Codificação_de_caracteres
would become:
http://pt.wikipedia.org/wiki/Codifica%C ... caracteres

My usual solution when BBCode doesn't like a given URL is to run it through http://tinyurl.com/.

Thanks for the tips, guys.