When I try entering a tweet through Twitter.com that starts with an asterisk, I get an error of "Sorry! We did something wrong", and the tweet does not get sent. The same thing happens if I use Tweetdeck.
To try this, send the following tweet: * test There is no problem using a single asterisk anywhere else in a tweet that I can find. -- 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