Seeing's how you've approached the topic of aesthetics, I'd like to offer an opinion, too. :o)
>This is pretty nifty.
>- like a lot your modifications to the typography
>- like how you highlight the pieces of (bad) code
Ditto.. The new highlighting offers some nice, simple "wow" that will appeal to novice users..
>but am not fond of / convinced by (yet)
>- the top banner (but I'm not objective, I like the tree/banana
Again ditto. Hope this comes out right. What the W3C is trying to do with regards to uniformatting the Internet is awesome. Unfortunately, from what I've seen as I travel an oddly mix~matched variety of sites each day, the group is sometimes seen as aloof, untouchable, very clinical. Those banners add some nice, uplifting life to the site that, IMHO, directly reflects a personal side to the myriad of W3C members working so diligently each and every day.
So that's a banana, huh? Saw it a few days ago ad couldn't figure out was it was. Grin.. One comment here is that maybe it could be moved to one side or the other as well as the text being moved to the opposite side. On my computer, one can barely read the "tor team" part of "Feedback: The W3C Validator Team" because the banana and its background create a visual~related accessibility issue (on smaller screens is my guess).
>- the fact that the revalidation box takes so much space, hence making the (in)valid banner too low - one has to scroll
A couple of quick keystrokes could put the (in)valid banner above everything since it's the meat of why everyone goes to that page anyway.. Yes, no..? Maybe just below the navigation menu? The other info could follow. As a regular user, I also like the old revalidation box layout because that it doesn't take up as much room on the page.
>- the "help wanted" paragraph takes a bit too much space - but making the text shorter is on my TODO list anyway