I'm sorry to break it to you but the sentence you just wrote doesn't contain any —s.
That’s true in the US layout, but on other layouts those can be reversed.
> for example in this HN edit box: - – —
They look the same in the HN edit box because the font is monospaced, but once posted they do look different.
I suspect it is more common to see in papers as you can type it with just "--" in LaTeX.
It's basically an extension of US International which can type every letter in all the Latin based alphabets and most of the common punctuations, including hyphens, hyphen-minuses, en-dashes, and em-dashed.
Never found room for all the Greek letters, though.
I have used emdash, typed this way for many years before LLMs. I had got the habit from mimicking my journalist father's writing style.
The Compose key is useful for many other symbols «×»÷₁²♥⋄•
Except you don’t. If you’re on an Apple OS, by default doing -- (two hyphens) auto-substitutes for an em-dash.
Also, the key combination isn’t even hard. Depending on the layout you’re using, it’s either ⌥- or ⌥⇧-. My fingers press that (and the appropriate combination for apostrophes too) without me having to think. Those ⌥ and ⇧ symbols (and many more) I have mapped to text snippets.
We’re using computers, these things are trivial to do and customise, you don’t have to “hunt” for anything.
Why should I waste time reading this link, when the "author" themselves didn't write and, probably not even read it themselves.