Microsoft Word does this too. I've recently started manually uncorrecting these corrections in my writing because of this new implication that I used Chat-GPT.

Still less obvious than the emails I see sent out which contain emojis, so maybe I'm overthinking things...

I mostly find myself uncorrecting it when I'm trying to document command line flags.

You can edit the list of autocorrect to remove any you don't want (or add new ones).

Also you can ctrl-z immediately after an autocorrect to undo it.

the dashes and the auto capitalization are awful for technical writing. The ctrl-z becomes painful and annoying very quickly. Would that Word supported markdown.

This is a ridiculous maladaptive behavior. Word has been replacing dashes forever, consequently it has been unintentionally ubiquitous in business writing forever. That this character ever became a heuristic for AI is silly.

My Mac doesn't -- at least not as far as I can tell.

A long press of - should give it as an option as well. Mine auto translates it but I can’t recall if I added it or not.

You will have turned off the function "use smart quotes and dashes" in the spelling & prediction settings.

No, it's on (by default I assume).

In certain places it does seem to do the substitution - Notes for example - but in comment boxes on here and (old) Reddit at least it doesn't.

It’s a per-app setting that sometimes needs to be set in the text field’s context menu. There’s also a few apps that just don’t integrate with the macOS text system.

Well, I see no way to set it in Chrome. A good reason to be a little suspicious of Reddit or HN posts with em-dashes IMO.

It does on Safari (Mac and iOS) by default on Reddit.

Probably under Edit → Substitutions. That’s where it usually is in apps.

There's also Option (+ Shift) + -.