Today you just go "Eh, text is Unicode" and any weird corner cases go in the Private Use Area bucket never to be seen again.
And in the 1980s you'd go "Eh, text is ASCII" and just tell office workers that too bad they can't have an emoticon in their email, try writing :) instead.
But just at that moment where Windows exploded and everybody was getting a PC with a graphical user interface there was that awkward moment where it seemed reasonable to act as though text was arbitrary indexes into a font and doesn't actually _mean_ anything except that a lot of the fonts map to ASCII. So now you can write [HN removes actually Emoji] but it doesn't mean [HN removed the same emoji here] it just looks that way on PCs with the exact same font.
And that mistake infected Microsoft Office and all of Windows. I wrote a presentation on a work PC in about 1995 and then my boss printed it from her work Mac, and on every single sheet of the presentation the trademark symbol was replaced by some other symbol Macs had because of this useless ambiguity.