I don't know how "harmless" the noise is - isn't it the clutch plates making the noise? I don't know how that could equate to no wear. Also, yes - it could arguably lower the resale value of the car.
Also "harmless" to the car or to the driver? Whenever the car starts acting up, the shifts become weird and jerky and I have to be super alert that I'm not going to rear-end someone in traffic. I wouldn't parallel park it when it's in a "mood."
Also, every time I take my foot off the brake or press the gas and release it (creeping in traffic) I hear *knock knock knock knock* - I don't know if that's the clutch doing something weird or the motor mount bouncing back and forth. Either way, I don't think it's good.
2012 FF Ti HB Kona Blue, DCT, Built 5/24/2011, 401A + Ti Handling Package, Parking Technology Package, Winter Package, Moonroof, and MFT w/NAV at v3.6 109k miles and counting...