ErekT - your code modifications make no sense, referring to property names that don't exist. It looks like it will have identical effect to set 'Sampling' to 'Point' in project properties, which sets linearSampling to false and turns it off, as opposed to accessing the non-existent pointSampling property which returns undefined which is probably also interpreted as false.
I still have no idea what people are talking about when they say things are jittery, and still nobody has provided a .capx to demonstrate. Everything has always worked perfectly from C2's side as far as I've ever seen. My best theory is that everything is working correctly and the perceived "jitter' is simply the difference between point and linear sampling. Linear sampling can look very smooth and elegant, especially when scrolling slowly, because it can render smoothly along sub-pixel positions. When you switch to point sampling, what you are telling Construct 2 to do is to turn off that lovely smooth linear sampling and revert to a nearest-neighbour filter. This can sometimes look comparitively "jumpy", since it will not render any sub-pixel positions - it will pick a side, and go with that. So scrolling slowly goes from a lovely smooth sub-pixel transition to occasional pixel-size jumps. I would agree this does not look so good, but by choosing point sampling you are literally asking for that to happen.
So in other words this is the normal, expected result in computer graphics. It's more to do with how digital rendering works than Construct 2 itself. That would also explain why 
Amanita has observed it in other tools.