That said, it is great to keep discussing not just the problem, but also possible solutions! I didn't meant to say I just wanted to keep complaining. Sorry if that's how my post came across. ^^;
Using different fonts is a good idea; thing is, I'm already doing that, and it's not enough. I also think there's been a bit of misunderstanding? The reason I mentioned the ancient Korea thing is not because I want the language to sound archaic. It's because the cultural differences are so huge; 1) body language doesn't carry across. 2) The flow of the conversation doesn't match. 3) etc etc etc.
For the most part, I stick with Korean body language for the "Korean" characters, but even then there are subtle deviations I make for the English-speaking audience. I would have to redraw those if I were to start releasing the Korean version again. There's simply no way around it that I can see.
The flow of the conversation is a different matter entirely. That, I'll just have to get better at writing dialogues; I just happen to have extra hurdles is all. For instance, when character A has something to say to character B and C, in American culture the most natural choice would be B first, then C... whereas in Korean culture, you might talk to C first, and not even address B at all until C is out of the conversation. (This doesn't always happen that way, but there are definitely situations where this happens.) Or something that's super simple to say in English becomes ridiculously long in Korean.
It's a pain, and there's no single magic solution that works with every scenario. Each scene, each line is different; every time you gotta make a judgment call and hope you've made the right decision!