Why are you guys bashing Mozilla so badly? They might have made a mistake, yes. But what about giving them some constructive criticism and/or some recommendations for ways to fix the situation instead of this bashing craze? I mean the liveliness of the web we feel so natural today wouldn't have been possible without them. But now that we have an arguably better browser (backed by a corporation that doesn't hold the users' privacy that important IMO), everyone is busy making fun of them, huh?

I also don't know the specifics but as I'm Korean myself, I think I can guess.

Korean IME behaves in 2 mutually exclusive modes - Korean(Hangul) & English. Usually toggling between those 2 modes is done via an additional key in the keyboard.

Suppose you're typing a document with both Korean and English text in it. Further suppose you just typed a lengthy English text, and forgot to press that Korean-English toggle key before typing in the next Korean word, "여기에서" (which means "here").

When you type in that word in English IME mode, the key sequence becomes "durldptj". On seeing that bizarre word, your word processor thinks, 'Hmm, it doesn't seem like English text at all. Let me see if it makes sense if it were typed in Korean IME mode,' and it does make sense in this case. So it automatically changes IME mode to Korean and change above sequence into Korean word.

This automatic IME mode toggling functionality is widely implemented in Korean word processors, so I guess this case is revolved around it. But it's just a guess^^.