I examined mine carefully after reading your comments and.. did you buy it directly from HHKB? Maybe you have some counterfeit?
But you may be right, I'm not such a keyboard aficionado, I only had a few mechanical keyboards and maybe my standards are too low (or rather, at level which keeps me happy).
But as somebody else noted if you found the holy grail please share.
Plastic case plus very loose tolerances on the switches = it rattles.
It's great if it doesn't bother you, it didn't really bother me until I got to experience better.
Even something as small as resting fingers on a key feels so much nicer when the switch has 0 play