Isn’t that effectively the same situation, only reversed? You’re making assumptions about what your audience understands and are asking them to cater to your communication style. And there certainly exist folks who wouldn’t know that μm is \{mu}m. In fact, plain old ASCII backslashes themselves are fraught to enter in many text widgets!
Here’s where it’s different: unicode is designed for people to communicate. Yes, it might take some effort to write unfamiliar characters. Yes, you might want to take care around confusables. But code is read far more than it’s written. So write for your audience.