You cannot type Chinese, Japanese on a Sign block. This is a serious problem for those who doesn't know English or for those who try to make a map for non-English speaking country. This bug has been researched by other countries forum and found where the errors are located: Client version (1.4.6)is located at iv.class, Server version or Bukkit (1.4.6)is located at NetServerHandler.class . However, I hope that this bug will be fixed in the future version, so that people who doesn't know English won't have to patch files every time they update Minecraft or wait until the patch is released.