Comment by heycam

I just did some poking around, and it looks like uBlock does insert a couple of <style> elements into the document. I'm not sure if this is how all style-based blocking is done in uBlock, but since these are document-level style sheets, they are not shared like user agent-level sheets are. (We will in the future be investigating whether we can share more data between common document-level style sheets across multiple documents, though.)