@Kilian Awaiting the blog post I am currently finishing, you can check the spec [^1] which has some info boxes on why you need `CSSNestedDeclarations`.
Mainly to fix the shifting up behavior but also some other side-effects from before.
I manually added the `specificity` and `resolvedSelectorText` attributes for demonstration purposes. Added a note in the demo itself to clarify that.
[^1]: https://drafts.csswg.org/css-nesting/#nested-declarations-rule
@bramus if you ever make a CSSWG proposal for that you have my +1 ;)