Ironically, I personally prefer good typography, but unless the editor for the desktop app is autocorrecting -- to —, I usually don't bother. But when I type on the phone with screen keyboard, I almost always do bother, even though entering text on mobile is objectively slower and more difficult and often with fewer options.

In this particular case, the options for mobile 'phone keyboards are greater rather than fewer. The em dash is a first class citizen on the "writer" layouts in ThumbKey, for example.

* https://github.com/dessalines/thumb-key