Comment by wink

Unfortunately this table doesn't show us where the em-dash users are coming from and if they are native speakers.

It's not that it doesn't exist in my native language, but I don't remember seeing them very often outside of print books, and I even know a couple typo nerds.

Maybe I'm totally off, and maybe it's the same as double spacing after a '.'. I had not heard of this until I was ~30 and then saw some Americans writing about it.