It is an en dash, not an em dash, since it's about as wide as an n.
Some software substitutes a double hyphen -- with an en dash rather than em, and use the triple hyphen --- for the em dash. Perhaps Hacker News' title formatter is one of them.
Okay, edit submitted, but that is extra weird, because the double hyphen is a convention or placeholder for an emdash. When a transformation takes place, it becomes an emdash.
There is no reason to transform it to an endash. I don't know any software that would do that. Checked with an LLM, too. That makes no sense at all!
TeX uses -- (double hyphen) for producing an en dash and --- (triple hyphen) for an em dash, and that's pretty darn longstanding and well-established. And FWIW, the English writing conventions that I learned use em dashes as punctuation without an adjoining space—like this—but allow en dashes surrounded by spaces as an alternative – like this – so I frequently see spaced double hyphen used as the ASCII equivalent of dash punctuation and interpret it as the latter. I've never personally heard of double hyphen for em specifically, only either as en specifically or as a sort of ambiguous whatever-dash.
LibreOffice is the same, double hyphen is en-dash and to get an em-dash you have to type:
:---:
I thought this was part of why it became an LLM signifier, most people can't tell the difference between the two visually and as far as I knew en-dash is what you usually get by accident, while LLMs use em-dash.
Then how do you type in an en dash instead? Also, according to LLMs, the en dash is used in far more languages than the em dash. Many languages don't use the em dash at all. Using the em dash for sentence interruptions seems to be specifically an US American English tradition: Most languages which use dashes for sentence interruptions use spaced en dashes instead.
I get en dash with alt+- and em dash with alt+shift+-. One of the niceties of the macOS keyboard layouts. There’s also the ellipsis and middot among other things.
Unless, you know, you configured it to work differently. I'm using [Compose]nd and [Compose]md . And a bunch of other cute things, like [Compose][Compose] for escape (with Caps Lock as my compose key).
From the title I've learned that git uses an em-dash instead of double dash as options delimiter. Thanks for pointing out that the title was wrong -- I've never had a need to use -- with git, so didn't know that it doesn't work.
Some software substitutes a double hyphen -- with an en dash rather than em, and use the triple hyphen --- for the em dash. Perhaps Hacker News' title formatter is one of them.