Use single quotes in your CSS and avoid double quotes and great than/less than signs in the CSS as they get caught in the filter. Haven't looked yet but I'm guessing the double quotes are why the attribute selector fails.

These are a wontfix because there exist workarounds that allow you to do almost anything, and the filter we have on it is necessary. I agree that there is room for improvement but it isn't a problem or priority right now.

The escapes might be an easy fix so I'll look into it if I have time :) It's just low priority since the feature still works correctly and there is a lot on my plate.