There is nothing in the feedback that would cause Ebay to remove it.
Your response makes it look worse.
When the buyer asked for a return, you surely know that the proper procedure would be to insist they open a case, send them a tracked label and refund upon receipt of the returned item. If you had done this, the buyer would have been refunded and might not have left a negative.
The buyer clearly feels cheated and I understand why.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)