I will admit I'm more like to use "--" and not bother converting it if not done automatically on quick forum posts. You can find examples in my post history. But I come across them all the time in written works.

Many of us who use em-dashes are so used to Word/etc correcting -- to — that it's just part of normal typing. I'm find if it renders either way, but I use -- in writing all the time.

One day this whole thing is going to read like the 1980's where you could tell if a latter was written by a "real" typist and not a word processor by the lack of correction liquid/tape.

But this is the problem, if you type double “-“ on iOS, it just turns it into an emdash. (“—“)