The ship has sailed, unfortunately. Obviously humans use em-dash too. But more and more people's first reaction to em-dash would be "haha got you, AI!"

Imaging you're an artist designing a character with 6 fingers today.

The situation is really sad. People who have the proper skills have to change how they work just to avoid "witch hunting" (for the lack of better term). What's next? If GPT-5.5 uses a lot of ellipses, are we going to stop using them? Semicolon? Will humans be using the most watered-down subset of English only at some point?