Giving feedback OR making a claim for money back is never dependent on doing what the seller asks or wants you to do. You're not at a seller's mercy.
Your mistake was to keep asking the seller for money back.
They obviously don't want to give a refund or they would have done so ages ago.
You say you have opened a case. I am not sure how it will go because it sounds as if you may be a bit outside ebay's time limits but it is worth doing as Digital ghost said and contacting ebay chat about this.
If the ebay claim does go ahead, keep an eye on it because if it is the same as it used to be, you have to finalise the claim after a few days, if the seller doesn't provide evidence of postage or arrival of the item etc
If you do get knocked back on the ebay claim because time has run out (which is no doubt what the seller is hoping for), then go into a paypal claim. You don't have to ask the seller for permission, just do it. Same deal there I think. You make the claim and confirm/finalise it a few days later. I know once when I made a paypal claim I had to wait a week in order for the seller to give a satisfactory reply. I am not sure if that is still the case.
A satisfactory reply is NOT, I will refund you later when you close this case. Or "I have just posted it so you can close it now".
Unless you have the money or the goods, you press ahead with your claim for a refund.
Don't worry too much about missing out on giving feedback, although in this case it's a pity, I know, that the seller has dodged a negative.
You can do as digital ghost suggested though and report the seller to ebay for feedback extortion. Ask ebay to view the relevant messages. That's as good a revenge as bad feedback.
