Very alarming.  I often do partial refunds for overpaid postage or for bulk pricing discounts and am also concerned that these customer service oriented business practices may actually be punished under the new defect system.  It's just counter intuitive, damaging to sellers and I can't see how it can be any help to buyers either if it results in sellers feeling reluctant to provide refunds/ returns etc to avoid a defect.  I did a partial refund today and I'm just waiting to see if it shows up as a defect.