Charles,

There's a link to eBay's FAQ feedback forum at the end of this message.

Review the rules for removing a feedback.
Question: Can negative feedback be removed?
Answer: If the comment meets ebay's guidelines for removal, it can be removed. Otherwise, you can try going through Square Trade to have the comment removed. There is a $15 fee, and both parties have to be in agreement to removing the comment.
You will see a link to eBay's rules for deleting feedback.

You can post a comment to his response.
Scroll down to the question:
Question: Can I respond to a comment that someone else left me?
Answer: Yes, you can respond to a comment that someone else has left you.
You will see a link for leaving you comment.

Dennis