Clever, but needs a lot of work. Larger comments with replies break the view on top a bunch of other tiny annoyances. After using it for 15 minutes it felt like those Star Trek consoles, where you need 6 key presses to put what you need on screen. Stopped working for me soon after going into a larger thread and realizing I kept losing my orientation on the comment tree, essentially forcing a jump into HN proper. IMO it might work better for Twitter.