Page Up in editor has odd effect
Focus is at top of page and at bottom of editor:
Hit Page Up once:
Hit Page Up a second time:
(Chrome bug where cursor is hidden behind top border of textarea is exhibited in this screenshot)
Once cursor is at top of editor, Page Up works as expected, moving the page view up instead of down.
Overview: Pressing "Page Up" while at the bottom of the editor jumps the page down similarly to pressing "Page Down" when not in the editor. Only happens while the cursor is not at the top of the post being written and possibly only when the editor has enough content to scroll.
What's it doing, if described in words instead of pictures?
The page jumps down like you're pressing Page Down instead of Page Up, and also the page is handling the Page Up press when only the editor should be (the same with the Page Down bug I reported).