The chat doesn‘t support even nearly all the letters that most of the languages have, for example the Kazakh letters Ә, Ғ, Қ, Ң, Ө, Ұ, Ү and Һ. Also some pre-revolutionary Russian letters: ѣ, ѵ and ѳ.
Also, the ALT codes don’t work. What I mean is that if you want to type for example these «quotation marks» on PC, you need to use Alt + 0171 for « and Alt + 0187 for ». Also to type —, you need to use Alt + 0151 but none of these is possible because the ALT codes don‘t work at all in Pixel Worlds.