I can see some Russian texts chat in the Official app running on Android 5.1... but I haven't see other non-English words besides Russian...
I tried typing Japanese but it doesn't work either, it appears blank in chat (but IDK if other player see the words I typed, I'll try again and ask other player to see it)...
also I always use external keyboard and mouse with my phone to play this but it seems that some characters can't be insert directly into the text input in game, like the search bar of inventory/creative or writing sign... the characters I noticed that aren't working are slash '/', backslash '\', plus '+'*, question '?', less '<' and more '>'... it did work if using popup (click on that text input brings another popup to write) but it didn't work when writing directly... the error shown is unexpected multibyte character, I use default Android keyboard in system when connecting external keyboard...
I hate that popup because it somehow pauses the game, everything else including chats will freeze when I'm typing inside the popup and it will be good again after I dismiss the popup either by clicking empty area (cancel typing) or by pressing 'enter' (confirm typing)...
*the plus key beside backspace doesn't work, but keypad one works in all situations.
When typing slash/ in the creative search text input, the / doesn't get input and error message thrown in chat...
When click at that search text input, it gives popup, in this popup I can write the slash/
and when confirm the text by pressing enter, the text written in popup shows up correctly in the text input