It's relatively common knowledge that the Chinese government blocks certain content in China. Most of this won't affect Chinese users. But does iChat censor messages with said content in them?
This Yahoo Answers question says that the content won't be blocked unless it's pornographic or politically extremist. However, I'm not sure if Apple lets China access their messages, so I'm not sure if the Chinese government could do this.
Unfortunately, I don't have a way to test this myself. I've done some research, and I haven't been able to find a definitive answer, thanks to the fact that I can't read Chinese.
Example: I send a message to person 1 in China saying 'Down with the government! Tank Man! Tibet! Liu Xiaobo! Tiananmen Square protests of 1989!' Does Person 1 get the message or not?
Best Answer
No - iChat has no provision for blocking or filtering what you do.
It does rely on DNS and thus is easily blocked by any network operator that chooses to do so. It is vulnerable to blocking of the major chat servers that let people know who else is online.