How do you tell when something was written by a person?

There's a Pew study out about how much of the internet is AI now, and it's got me thinking about the actual tell, not the statistics. In my line of work I spend hours listening for the tiny imperfections that make a take feel alive. What's the giveaway for you — a turn of phrase, a weirdly specific detail, or just that feeling in your gut that something's off?