I have lived in Korea and Japan. Minecraft is HUGE among people there despite this problem. It is really really in Minecraft's best interest to prioritize this problem. Download a Korean or Japanese IME. Try to type anything (especially 漢字). The IME eats keyboard input before deciding which characters to spit out either when one presses space or enter. Minecraft does not allow this.

All other computer games by Microsoft as well as multiple mods have found a way to allow this. Solution - look at whatever basic programming trick the mods did or call your bros at another Microsoft department and implement IME language input into the next update.

Cheers.