Irony an article written by AI, wants to say do not use AI for writing. Following sentence looks like written by an AI, human do not use double dash, it seems AI instead of emdash wrote double dash;

“I think you should almost never use AI to write -- that is, to do the thing you’re doing when you type words on a page -- whether for a blog post, a research report, a memo,”

This absolutely doesn't look like AI writing and this is a pretty weird signal to use.

I have a much better theory: as it happens, Substack automatically converts "--" to em-dash as you type. I'm guessing the author knew that and wanted to use this feature, but composed the article in another editor and then copied-and-pasted the whole thing. Because of how Substack implements the feature, the substitution doesn't actually kick in on Ctrl-V, so all these "--" remained in place.

Haha, I do actually use double dash, as I write in org-mode. I then convert that org-mode text to Markdown and copy and paste the Markdown into the Substack editor, which preserves the double dash. In case it needs to be said, the article is 100% human-written.