I'm guessing that it's something to bear in mind when you get your Tern, make sure the hinges are correctly tensioned from the very start. Not sure sure how exactly you do that, but if there's any sign of the latches being a bit too free then adjust them, and perhaps you'll eliminate any slight slippage that wears away the powdercoat and ends with creaks.
I realize now that my Dahon frame latch would have been better off being slightly tigher from the start, but there was no play or looseness to indicate it should have been. Just that it developed creaks which I suppress with a bit of grease. Which attracts dirt and abrades the powdercoat no doubt. Oops.