> assume

There's your trouble. The real problem is that most internet users are setting their baseline for "standard issue human writing" at exactly the level they themselves write. The problem is that more and more people do not draw a line between casual/professional writing, and as such balk at very normal professional writing as potentially AI-driven.

Blame OS developers for making it easy—SO easy!—to add all manner of special characters while typing if you wish, but the use of those characters, once they were within easy reach, grew well before AI writing became a widespread thing. If it hadn't, would AI be using it so much now?