Right now if you flick a two-finger scroll upwards, take your fingers off the trackpad and hit control, Windows (tragically) appears to handle "momentum" by continuing to send standard scroll-up commands in some steadily decreasing frequency, rather than treating them as separate kind of event.

So if you hit control before it's done momentum-scrolling, all of a sudden that turns into a rapid sequence of zoom-in or zoom-out commands depending on the direction, and your browsing experience does something insane for less than obvious reasons.

I propose that we ignore control-scrollup and control-scrolldown events either completely, or for some nominal period after a non-ctrl scrollup event has happened. ctrl+ and ctrl- both serve the same function, but are more predictable and much harder to accidentally invoke.