Isn’t that an endash? - versus —?

Something weird is going on, on iOS I can type either but they look the same in my comment.

Edit: Only before pressing reply. Once posted they look different.

You're right, I had a similar issue with the form.

I always have been using em-dashes with specific spacing:

1. replacing parentheses —given that the em-dash in pairs for me mark more-relevant-to-the-main content than a parenthesized expression would— so I use the same spacing as `()`

2. replacing colon or just finishing the sentence with a subsentence— so the spacing goes like for a colon.

Probably unfounded grammatically and against any style guides, but this spacing makes sense to me.

I am pretty sure an em-dash in case 2 should not have spaces in either side.

Yeah, LLMs seem to use it closer to a semicolon than a set of parentheses, which seems a bit more "fancy"/"inauthentic" IMO.

That's a good point! I nearly always use it in pairs.