I'll try to make the backstory as brief as possible here.
On July 15 (a Thursday) I placed an order for a textbook through the fractionally named subsidiary of a well-known online auction site. On July 19 (the Monday following) I received an automated notification from the site that my order had been shipped, with a tracking number. Unfortunately, when I used the tracking number at the shipper's site, it showed as no record of the item. Initially I figured the package has simply not been scanned it at pick-up as I've seen this happen with delivery confirmation before. When I still did not have delivery by July 29 (Thursday) however I became a bit concerned, as my experience has been that even media mail usually delivers in less than a week, especially when coming from only a few states away as this was. I was beginning to suspect that this book never made it to the shipper, and I decided to check the tracking one more time before contacting the seller. This time the number was in the shipper's system, showing as received by the shipper on July 26. The book was delivered the next day, Friday, July 30. It had been shipped in an unpadded mailer, which had torn open in transit (this was a 1700+ page textbook) and was held together by rubberbands wrapped around it by the shipper.
So, to summarize, a book that I ordered on July 15 was not shipped until July 26, with no communication from the seller about the delay, and the packaging of the shipment was insufficient. After deliberating with myself considerably, I opted not to contact the seller about my displeasure, as there was nothing to be done to correct the situation. I left negative feedback, the first time I have ever done so in my 7 years of using this site, stating that "Ordered & pd 07/15/10, shipped 07/26/10. Poorly packed, unpadded envelope ripped."
Now, to my question. Today I received an email from the seller, "I just saw your negative feedback you have left for me on my account. I am terribly sorry to hear this! USPS has been letting me down lately, however I must take the responsibility. Would a 20% discount rectify the issue? Again, I am so sorry you are not happy. I cannot accept negative feedback from my customers. I hope to hear from you soon."
How do I respond to this? The problem did NOT lie within the shipper, it was solely with him. He did not ship the package in a timely manner, and he did not package it properly. A discount cannot in fact rectify this. What is done is done.