Is the amount of em dashes counted or the comments that have at least one em dash inside them?
You know, I am asking for...science(?).
I also wanted to point out that these could be Kantonese/Mandarin/Japanese/SouthEast Asian users that use their local keymapping software because a lot of them use the idiom symbols (e.g. the dot character, too) when they switch to the English keymaps.
Check out how laptops usually look like over there, a lot of manufacturers build that right into the firmware.