This one might be a bit tough to explain:
Turn on soft wrapping for a language, and open a file of that language that has a line long enough to activate the soft-wrapping. Grab the vertical scroll bar's handle with your mouse and drag it down. Keep dragging your mouse pointer down past the bottom of the window, and you'll see the handle move to the bottom of the buffer, but as the mouse goes past the bottom of the window, the handle jumps up a bit, so the bottom of the buffer is back at the bottom of the window. It's sort of a jarring transition.
