> Unicode was introduced to solve that very problem, and it largely does.

What? Unicode doesn't address the problem at all. Your emoji password will look completely different depending on the encoding you use. We have multiple popular encodings right now... but instead of software that lets us specify which encoding we want to use to interpret a document, we have software that intentionally prohibits us from doing that because it's supposed to be a security risk.

UTF-8 wasn't introduced to solve the problem of there being multiple encodings of any given text, either. It was introduced to be another encoding.

> In a fictional ASCII world, Apple could have decided to remove the Yen key from the Japanese lockscreen keyboard.

That would have had no effect other than momentary user confusion. In that world, someone with a yen sign in their password would, after the keyboard update, have a backslash in their password, because their password never changed. Only the label changed.

In this world, though, it's still true that the password never changed. But what did change was that Apple implemented specific logic to prevent people from entering that password. The label didn't matter.

(And the article is ambiguous over whether the appearance of the keyboard changed or not. It's not ambiguous over whether the behavior of the keyboard changed -- it didn't:

>> Post-update, when entering the passcode, the keyboard now displays an identical accent mark in the háček's place, a feature Byrne described as "pointless; they're encoded the same."

There may or may not have been a cosmetic change to the keyboard, but there certainly was a change to the behavior of the password field.)