This happened a few weeks back when I tried to flip around between English and Thai language setup. And it happened couple of times. I thought I could always warn the customer to use the same language setup before they login the system, so I gave it a lower priority.
But today, when i try to reproduce the same issue, it does not happen. Maybe I haven’t got the environment setup right.
Nonetheless, this is necessary in my case. When one user is typing unicode language like Thai under Thai language setup, he can type and see Thai characters nicely. But if another user is connecting to the system with a different language setup like English, he wont be able to see or type Thai, the Thai characters are shown as unreadable strings. So, a check to make sure this setup is consistent across all clients makes sense.
I will give it a try later, thanks a lot andrew!