Site from the watermark:

Yeah, somehow it looked AI before I clicked into it for the high res version, something about the way the guy's face was drawn. And when I saw the high res, it was really obvious, because the pupils are askew in a way a true artist would not have chosen. And as you say, the stippling pattern is typical of AI. Weird that our brains seem to be some of the best competitors in the arms race between creating and identifying AI images.

The top right one is definitely not drawn by a human, it's right out hexagons. Noone cross-hatches like that because you can't cross-hatch like that there's no lines going straight through.

The rest could be artistic choice, compression artifacts, or other stuff though. Well, some minor stuff, the topmost book on the left pile on the desk on the right is sus, and there's way too many sponges at the base of the chalkboard. But none of them are dead tells like the hexagons.

This looks shopped — I can tell from some of the pixels, and from seeing quite a few shops in my time.

I was thinking so as well. Mostly because of the left pupil not looking like the right pupil, but also the style. The style of shadow below the chalkboard looks like a really odd choice.

How did you spot that? I'm good at spotting real life images but I didn't even blink at this one. I saw one thing when I went back after reading your comment, but it took me a minute to find it

Hmm, maybe. I honestly can't tell.

Dihydrogen monoxide?

It seems Hydrogen dioxide is pretty deadly too. We’re all fucking doomed.

You're not wrong about that.