| I think I might be able to shed some light on this issue. I had a civic type R for a while and was an avid forum member. The "Chewbacca noise" was a well reported issue on the car and many people tried (mostly in vain) to get it fixed under warranty. Those who did get a new clutch plate under warranty were often disapointed to find the issue still present, though perhaps to a lesser degree.
When trying to get my car fixed under warranty for this very issue got a phone call from Honda UK's technical department who gave me a description of what the noise was and why it happened. He told me that the noise occurs due to differential expansion of the clutch pressure plate and friction material. Obviously this isn't repairable and really is just a combination of design tolerances, different metals and thermal effects. It also explains why some get the issue more or less dependant on ambient temp or engine temps.
I have had the issue twice on my car when changing down into 2nd enthusiastically and confirm its the same noise and presumably same cause. Still, if they really knew what caused it they'd address it, so some of it is guesswork/vagueness.
It really boils down to sloppy design.  | 
