Yes I understand, but I wouldn't want that in a chrome extension personally. It could make styling harder. When you nuke rules without considering specificity it can cause unintended consequences. If everything just followed regular CSS rules as if all CSS was applied by the author there would be less of a chance of changing something you hadn't intended to change.
The people who use user style sheets (especially !important rules) in CSS aren't particularly interested in your styling. They're interested in the content in a style that works for them.
This is an important accessibility feature of CSS and I'm disturbed at any reduction in support for this feature.
