TL;DRSpitters and worms being tricked by twitchy movements can be fixed by using short-term average character speed instead of momentary speed for prediction.
What ?Currently, if you're running in a straight line, worms and spitters predict your position and still hit you. That makes them a stronger enemy which is a good thing. You can trick their predictive aim by running in a zig-zag pattern, which is also nice - it requires some skill and attention.
However, there's another way of making the worms miss most of the time, that's easy to execute and looks kind of stupid: quickly pressing A and D (or S and W). The aim goes way off because any moment you're running to the side, but you actually stay in the same place and shoot the biter nests as if it's not a big deal.
The worms could become slightly smarter if they averaged your speed used for prediction across several game ticks (~10-20 maybe?). That way they'll be still pretty accurate when you're too slow to change the direction of your movements, but won't be tricked by standing in the same spot and just pretending to be running.