I wrote an RFC about scoping Common.css and Mobile.css: https://www.mediawiki.org/wiki/Requests_for_comment/Scoping_site_CSS
In short: this could help us separate CSS rules added by administrators from the core UI rules of MediaWiki.
What we would get: * UI (chrome) CSS more predictable and broken less often * no crazy UI styling as seen at https://nv.wikipedia.org
Please share your thoughts.