I saw this bug reported for a single site here, but then I noticed it on another site, then another and another. Soon the list expanded to "most sites with a design". On many sites it's gone unreported.
Here is a list of sites that I think have pretty noticeable flaws because the Code of Conduct banner is pushing the content of the site down, but not the background. I don't have time to explain or screenshot the problem on every single sight on the list (not right now at least, though I'd really appreciate help editing).
I understand that the idea behind the massive redesign is to fix problems like these but a lot of these problems are too severe to wait (in particular, the UX site is practically unusable right now without dismissing the banner because you can't see any of the links to places like "questions").
In addition, some of the designs are affected by the increased top bar height, where dismissing the banner doesn't quite fix things completely. I now think this is the cause of another bug that I reported on UX, for example.
Graphic Design is not included on this list because it's a slightly different problem. In any case, I reported it separately here.
This bug affects a number of other sites that I decided not to list, such as the Cooking site, because it's hardly noticeable there. You could call it a literal "subtle putdown" :P