I tried, as a test, to type in Chinese in the game's chatbox. It does not recognize all characters. Some character will work, while others will display gibberish. I don't think the game's UI or codes likes Chinese at all.

I think Taiwanese players can probably register in the Chinese servers (they can get the Taiwan compatriot passport which is basically their ID in China), to fulfill their ID requirement and all that...

Simplified Chinese isn't hard to read, but it does take some doing. Problem is communicating, especially newbie players who don't know the mechanic and is dragging everyone down. I can't type "stay away from the orange area" or "go to the corner of the map when zeromus does his thing" fast enough when seconds count.