Yes, this FR already exists with plenty of discussion, and I’m going to merge your post there.
Bike Outliner is an interesting note-taking app. I believe it is rich-text formatting though. It hides any syntax characters, and he calls it “Typing Affinity”. When you are editing at the border of a format, it has a special caret that points left or right so you know which section of the formatting you are editing into.
