I was recently reading through the input handling code for firefox on windows. Turns out that some input method editors insert a special character that facebook

I was recently reading through the input handling code for firefox on windows. Turns out that some input method editors insert a special character that facebook then deletes, breaking input handling. So they have a special case fix for facebook where they turn that character into a different one. I guess when you don't have enough market share to force extremely popular websites to fix themselves, you're forced to fix them yourself.