One additional point: Right now I can press Page-_Down_, or Scroll-_Down_, but have to press Arrow-_Up_. I fail to see how this is logically consistent with a single mental model.

Making both work might make sense, though honestly I'd be surprised if users actually try to press Arrow-Up to see the panel.

This seems like the kind of thing to throw a few quick hallway tests at.

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Erik Möller
VP of Engineering and Product Development, Wikimedia Foundation