My Brompton (M6R) doesn't rattle at all. I also don't consider myself a "privileged member of an elite group". I consider myself a savvy purchaser who did my research (I test rode Bromptons, Dahons and Terns) and was willing to pay a little more for the quality, fold, ease of packing when traveling and resale value that I found in a Brompton.
I've had 6 Bromptons and they were all solidly built. I'm out of that market now because my arthritic wrists can't handle the bar shape anymore and swapping to what I need would compromise the fold, but they're great bikes.