It annoys me greatly that correct punctuation can be make your work look artificially generated.
"it looked like a real message but the dot at the end gave it away"
There are similar opinions with artists too. Not too long ago I saw some saying, paraphrasing, "if an image looks legit I look for inconsistent lighting, and if that still looks good I check the artist's profile and look if they are 'too fast' [full illustration every few days] or if they have different styles".
I haven't seen anything like that with code, but I wouldn't be surprised if someone said that human-written code is actually AI-generated just because the structure looks weird to the reviewer, or because it has some "what" comments (instead of "why" comments; both have their place), or things like that.
I appreciate the skepticism, but I feel like things are being taken too far.
Plagiarism has a long history, and the options are numerous, including using some other student's prior work, or paying a human "homework mill" overseas to research write your report for you. It's usually the differential in styles that will get you noticed, because a teacher gets to know their students and what they're capable of in the classroom.
Also, using a hyphen instead of an em dash isn't "incorrect"; it's a traditional way of writing, because most of us grew up with ASCII, and only the one key on our keyboards. Only a journalism or literature class would be concerned with teaching the distinction and marking points for using those.
I could list about 5-6 signals of LLM generation that I've noticed. Proceeding to investigations and accusations is discretionary, and shouldn't be taken lightly.