ah that's a shame. Feedback basically shows the reputation of seller (but I would like to say we're community member).
I personally disagree with this rule. Rules like the make room to make loop hole in system. Like other members suggested capping the price at 1 rs just to get the feedback as per rule or talking only shipping charges, which is bad.
I also agree, and say if someone was promised publicly something in a giveaway but they never got it, should they get a negative feedback?