Of note is theother terrible heuristic I've seen thrown around, where "emojis = AI", and now the "if you use not X, but Y = AI".
Similarly: "The indication for machine-generated text isn't symbolic. It's structural." I always liked this writing device, but I've seen people label it artificial.
Em-dashes are completely innocent. “Not X but Y” is some lame rhetorical device, I’m glad it is catching strays.
With the right context both are pretty good actually.
I think the emoji one is most pronounced in bullet point lists. AI loves to add an emoji to bullet points. I guess they got it from lists in hip GitHub projects.
The other one is not as strong but if the "not X but Y" is somewhat nonsensical or unnecessary this is very strong indicator it's AI.