Doing it right (via the algorithm above) is a trivial few lines of code. The thinking behind the state machine that gives both high reliability and low latency

Doing it right (via the algorithm above) is a trivial few lines of code. The thinking behind the state machine that gives both high reliability and low latency isn't trivial. It is, however, obvious once you know the trick of maintaining an extra auxiliary variable in addition to counter/timer variables, and understand that you don't need to wait for the bouncing to finish before registering a change. Think sort algorithms; everyone comes up with bubblesort first, but you can do much, much better with only tiny changes after a bit of thought.