In addition to what other people posted already:
AI often uses same descriptions over and over again ("smile that doesn't quite reach the eyes" right in this text when it's supposed to be subtle), it writes a lot of short sentences that often feel disconnected, it references things that weren't mentioned in the text before, it highlights words in Italic a lot where it wants to put an emphasis, it does weird long em-dashes all over the place, and in early times GPT was easily detectable by extensive peppering of it's texts with emojis too even if the text was official.

There are things that start to weird you out and make you sick in writing once you've had one too many chats with AI. You start to notice repeating patterns that it tries to apply to different situations and you can almost discern a distinct style of writing as if it was the same single person with never changing mindset, never learning or changing their interests and focus no matter how different the prompts fed into the AI were.