If you felt that packing peanuts would have prevented the damage, then the seller did not pack well enough and feedback is appropriate even if you call it a neutral. Most sellers know you have to pack for the "handling" after it leaves your hands.
I buy and sell on ebay and am pretty picky about packaging. Once I bought dishes from a reputable seller and they arrived only wrapped with Christmas and Thanksgiving napkins between the plates (and broken) I contacted seller and was refunded. I wondered, was she just that lucky on all of her previous shipments. Now I request sufficient or even extra packing up front.