alt Hacker NewsWell, I definitely never saw nearly as many emdashes a few years ago. I didn't even realize it wasn't just a typeface quirk as I'd used hyphens a lot. I don't even know how to type an emdash on my devices and would have to copy/paste it from somewhere.
But yes your other points are absolutely right
Oh yeah, emdashes are absolutely a tell, but I argue that they're nowhere near as abhorrent to read than the awkward phrasing that the frontier models like to use.