I don't think that's the entire story. I heard about the study from some German YouTuber. They spent several days writing the script for a video until the text was perfect (from their perspective). And that made their audience think they turned to AI assistance. So... Seems it both makes people think there's AI at work: Flaws in it, or being too flawless.

Idk. And from skimming the study, I gather you can train an AI to write exactly with the right amount of contractions etc, so we're F-ed anyway.

I take something being overly bland, repetitive or smooth in a weird way as indicators as well. After that I'll look at ChatGPT's distinctive idiosyncrasies. I think I'm not too bad at it, but sometimes it's really difficult. Even more so with some styles of images. Like pop art. I wouldn't know if something was made by AI or an artist. I mean by the image itself. I can probably tell if there's some layers of meaning in it, or if it's just some random thing depicted. (Once I'm educated enough about the context.)