It’s certainly hard to detect in isolation, but the thing that gives it away is the comment history.
All the AI acounts I’ve seen repeatedly post the exact same cookie cutter top-level comments over and over again. Typically some vapid observation followed by an obviously forced question serving as engagement bait. The paragraphs and sentence structure even looks visually similar across comments when you scroll down the history page.
Just look at a few of these accounts and you’ll easily be able to recognize AI posts on your own.