As someone who writes lengthy posts with dashes (see my post history) the text in OP’s screenshot is probably not out of an LLM.

There are zero em dashes, three compressed double-dashes, and four single dashes all used in the same casual way to break the flow of text, along with some ellipses and numerous grammatical inconsistencies/informalities which indicate that’s just how they write.

But they’re all different. Just so you know,

This is an em dash (note its length): —
This is an en dash (slightly shorter, but still longer than a regular dash, and has specific uses): –
This is a regular dash, the one on your keyboard: -

And different from them all, the compressed double dash. That’s what’s in OP’s screenshot, and they’re what you get on Lemmy and Reddit when you type two dashes together with no spaces between, and it passes for the em dash in human writing.

This is a compressed double-dash: –

Here on Lemmy, it looks exactly the same as an en dash, and that’s the tell: no one really uses en dashes outside specific circumstances like a parenthetical range of numbers, and why would they? En dashes are a pain in the ass. I don’t even know the keyboard shortcut for them.

But regardless of whatever else it may look like, a compressed double dash (–) is always shorter than a real em dash (—).

You can always look at the source of a comment (the little paper icon under it) to know which has been used. The only real em dashes in my online writing ever come from material copied from a source that uses them, because I don’t, at least not online.

Also, LLMs will generally employ em dashes in the old style (think books published on paper during the 19th and 20th centuries) where there is no space between the em dash and the letter it follows, like this— but I find that irritating, because visually it breaks a sentence like someone vocally stopping themselves mid-phrase. So I never do it myself, and most human writers do not anymore (though there are some) and generally it hasn’t been the style for at least twenty, thirty years now though you’ll see it in older publications like The New Yorker where their style guide hasn’t changed since the 1930s.

Rather, a human writer will generally employ an em dash — or a compressed double dash – with spaces before and after, or at least after. Like I just did. Look at the source, see it for yourself.

As someone who has written with em dashes for well over forty years I want them back, goddammit.