I've noticed on several occasions that text written by Mac users and published online would replace the Swedish letters ä and ö with a¨ and o¨. I think it's due

I've noticed on several occasions that text written by Mac users and published online would replace the Swedish letters ä and ö with a¨ and o¨. I think it's due to some combination of how they do Unicode normalization and how Firefox on Windows renders the text. I haven't seen it for at least a year, so I'm guessing it's resolved now.