Reference http://forum.square-enix.com/ffxiv/t...nguage-Support

The problem is the UI font for the NA/EU/JP client does not contain all of the characters to support Chinese text. You can type in Chinese or Japanese in the client by tabbing out and changing the input language for Windows, but you are limited by the font's character set. Here is some more information about the font created for FFXIV's UI: http://typeproject.com/interviews/square-enix.