The main place I encounter the highlights currently are in test files where it's expected:

I find myself often getting distracted by the scroll bar and minimap decorations, thinking I have real warnings in the file. I'd argue these warnings are mainly useful when you're actually looking at the code so am proposing not adding the decorations to the side for unicode highlighting.

If this happens, I'm also not sure whether there would need to be a setting for this. A less loud appearance seems like it would be better and sufficient.