The em-dash thing really annoys me. Using them has been house style the last couple of places I worked and I'm not just going to stop using them because some idiot might think they were generated by AI.

I think he's talking about it more in the sense that there will be speculation about the provenance of some work.

For example, if desktop fabrication tools get cheap and good enough, maybe one day garage tinkerers will be making Patek knock offs that an expert with a loupe, spectrometer, and a lot of time can't definitively say that any particular watch made after 2034 (to pick a date) is genuine. That would cause a lot of confusion and speculation in the market for used watches.

I think that's what his crypto bros comment was all about (aside from being a joke). Maybe crypto tech could provide evidence to support provenance claims?

This is a terrible analogy.

It's quite clear that the author means AI writing is now good enough to cause confusion and speculation as to whether a given piece of writing was human-authored.

The confusion and speculation caused by your nude transit adventure is about what the hell you're doing and why.

You're misunderstanding ... that's not at all the claim. Confusion and speculation is a consequence, not an indicator. Running around naked in traffic might well cause confusion and speculation, but it wouldn't cause anyone to confuse you with an automobile or result in speculation that are one.

At least AI is better at reading than are most people.

Again - did you even read the article you are commenting on? The author gives an example of a novel that had a huge advance offered on it and then pulled because of AI concerns... in order to get to the point of having the offer a bunch of competent writers, editors etc didn't notice.