HZPiano It's not exactly related to your discussion but for the recent days I've been developing (in my head) a design for a digital piano action that would have real (double) escapement, so that it will feel like a real grand piano action and inherently solve this problem of constant push back. My idea (of course just for fun for the moment) is to come up with a design that is not expensive and doesn't use wood nor require complicated mechanical design, yet achieve the same effect as a grand piano action. I think no digital piano company thought about that because they always followed the simplest possible design which comes from the fact there are no strings in real pianos, hence no need for escapement. It's a pretty valid argument and we've reached a stage where digital pianos are very good, expressive and so close to the real thing for most people. However I think a lucky coincidence of having real escapement and aftertouch in real pianos makes them very relaxing to play. To achieve that same effect, digital piano actions may have to employ similar means.
What I mean. On a real grand piano action, slightly before the key bottoms out, the hammer is detached from the key, it hits the string, rebounds and is caught by the back-check in the rear of the key. What is important here is that when it is caught, the 1:5 leverage is not engaged anymore and the kinetic energy (the shock) of the hammer is not transferred through the knuckle but is instead caught by the back of the key. This makes the shock experienced by your fingers from catching the rebounding hammer much less pronounced than if the hammer wasn't detached.
Now, continuing from the previous point, on digital pianos, since the constant shock from the hammers is always transferred through the same leverage and because the hammer rebound often coincides with you releasing the keys, it leads to the feeling of hammers always pushing back against your fingers. IMO it's not the end of the world but I think it's tiring at the least. But furthermore, I would speculate this push against your fingers doesn't allow them to relax before the next strike and this ultimately leads to lowered precision with dynamics. This is especially pronounced with the trills where the punching-bag effect of the static leverage hammer-key system (one with no escapement) makes the entire key-hammer assembly moving hastily and even accelerating uncontrollably. I've noticed my trills on digital pianos are just too bad compared to my N1X or acoustic pianos.
With all that in mind, I think the effects can still be recreated on a digital piano action, with similar mechanical devices but with no need to use exactly the same overcomplicated and expensive stuff like jack, whippen, double-repetition-lever, back-checks, etc.
