Uhhh, really? You can write and leave physical notes and almost anything else anonymously. You could "potentially" get something published anonymously. Artwork. Photos. You can play music anonymously. Wearing disguises in real life also isn't necessarily illegal either.

And it's worth remembering that just because your face or person is visible doesn't mean your name is. Or your home address. Being anonymous doesn't necessarily require "total" invisibility.

What it's mainly about is whether or not you want to share/reveal vital personally identifying details.