Seems to me this is a common problem with those RF boards? Not a valid vimeo URL Here's a dudes fix. I was going to recommend adding some pads and possible lube/silencing band? I feel like that would solve the problem.
I've had like 4 diff HHKBs and haven't particularly noticed this problem (stock-wise).
However, pbt spacebar, lube, and bands seem to make the boards more quiet.
I personally wouldn't let this potential issue stop me from buying a RF or HHKB. I would just try and purchase something used to try out. Then if you don't like it, just re-sell it for what you paid.