He made it hidden text in the assignment, i.e im guessing he made the text the same color as the background. Only when one copied the text and pasted it as instructions for a prompt would it be seen. Hence it was a Trojan horse on the assignment where those not using ai blatantly would not find it.

I'm not assuming a damn thing. He literally made it impossible to see the reference to Marxism unless you copy pasted the text in to another field. Like you would do if you were feeding it to an AI. Think very small white font.

Don't do this to me.

(Jokes aside thank you)

He definitely caught a number of them, but he called it proof, it should NOT be treated as proof, an indicator at best. If it were proof he could just fail them all and not catch false positives.

So you frequently wrote your papers from a Marxists perspective randomly when it had no relevance to the topic at hand? He hid the text by making it the same color as the background in the assignment so only when one copy and pasted the assignment or attached the file to their prompt would it be picked up. The only real false positives would be those staunchly Marxists students or someone using a screen reader. Which I think if you are inserting Marxism into random essays that are not relevant you probably are going to be bringing it up constantly in every setting you can and would also be able to explain it. It definitely is a reason to be failed on an assignment if he caught you with this.