[kelnos]

A double-dash is a perfectly valid substitute for an em dash given that most (no?) keyboards have it on a key. Seems like a waste of time to always have to look up an escape code or copy/paste from somewhere when the intent of "--" is clear.

[idoh]

I don't hold random comments on the internet to the highest standard because I am not a monster. However they are not equivalent and the em dash is a sign of extra polish.

[Veen]

It’s option-shift-hyphen on a Mac. And you can get at em dashes on an iOS keyboard by long pressing the hyphen. Not so difficult.

[SAI_Peregrinus]

Compose--- on anything with a compose key. Linux mostly and Windows with the WinCompose program.