Update: It seems to be the double dash -- within the ACE prefix of the punycode (xn--) of the international domain name that the Tweet button doesn't like. I don't know why double dashes are rejected. Anyhow, it would appear that if strings containing the ACE prefix "xn--" are accepted - perhaps as an exception to the blanket rejection of double dashes - international domain names would work correctly with the tweet button.
See: http://tools.ietf.org/html/rfc3490 http://www.atm.tut.fi/list-archive/ietf-announce/msg13572.html Cheers. -- Twitter developer documentation and resources: http://dev.twitter.com/doc API updates via Twitter: http://twitter.com/twitterapi Issues/Enhancements Tracker: http://code.google.com/p/twitter-api/issues/list Change your membership to this group: http://groups.google.com/group/twitter-development-talk