> some of the AI slop I’ve received from students include other fancy Unicode characters... that are difficult to type...

This is the bit I'd still caution against. Yes AI does this, but also writing in some software will correct 1/2 to ½, writing in tools that support MathJax will give you nice greek letters, etc. At university I spent days setting up nice LaTeX setups so that I could get good looking documents, including documents that didn't immediately appear to be LaTeX authored.

I think it's best to focus on the content, the writing quality, whether it targets the right audience, and whether it answers the question or just features a lot of words in the right ballpark. Focusing on the specific words and mechanical features of the text is going to catch out the wrong students, and it's going to be harder to justify from your perspective because you can't score a student badly for using an esoteric unicode character.