Lou wrote: "I don't think you provide any feedback under these circumstances. No harm was done, but no deal was done either. You aren't required to post a feedback."
I respectfully disagree, except in that you aren't ever required to post feedback. Let's say that an ebay item is shipped with internal damage which is unknown to either party, damage, and which the buyer later discovers. The seller says, "No problem, I'll stand behind it, and give you a refund," even though the item was advertised, "used, as is."
IMO, such a seller deserves positive feedback, because he has acted with integrity, even though ultimately, "no deal was done".
If I buy a product at a store, and later return it, for whatever reason, and the store is courteous and helpful in giving me a refund, that store notches up in my estimation. In other words, I had a positive experience, and, again IMO, positive experience deserves positive feedback.
Another 0.02 -- or less -- worth.