Doesn't inertial scrolling refer to the scrollable area keeping on scrolling when you drag a bit and let go? And accelerating if you drag it "more"? (Like iOS table views do.)
It's great to get almost fullscreen photos in chrome, but scrolling the text feels a bit tiresome. Pgdn helps a bit, but then the text ends up in an arbitrary position most times. If pgdn == new image, and pgdn again == comment on top of new image, and pgdn a third time == new image again, then that would be optimal. This is nitpicking though. This is a beautiful way to showcase your photos.
I made it so you have to scroll the text a little bit further so that the photo would stay pinned down long enough that you could see it, and scroll horizontally to the other photos. You're right, though, that page up/down (and arrow keys) would be a nice way to nav also.