How can people tell something written is AI?

I'm not a huge fan of AI and ChatGPT and robots and such. It reminds me of Smart House, and that's scary for me.

But, I do gosh dang love to read random reddit posts and comment chains. It's a weird cleanse, like reading gossip magazines back in the day.

I see responses of fellow redditors that seem to generally agree in many situations, that the OP is 'AI' written. I believe them wholeheartedly, especially if it is an agreed upon consensus.

My question, as someone that has no idea how any of the GPT(?)/AI tools work is: how can you tell?

It seems to be crazy obvious to some folks, but I don't have that sort of truesight enabled.

What are the signs, the tip-offs, indications?

I've definitely seen AI images where people have 2 right hands, or a pose that isn't physically possible, and can usually catch visual AI usage.

How can you tell an AI written post vs a realsies person post? I am so so curious, and want to gain the wizard keenness to tell them apart also.