That's really lousy advice, why are people determined to upset buyers?  It only ends badly for the seller.

Everyone changes their mind occasionally.  At least the buyer had the decency to let you know instead of it dragging out for the 8 days it takes for and UPI case to wind up.  You can relist immediately with a mutual cancellation, or even offer the item to another bidder if there was any.

If you select reason for cancellation  - buyer changed mind (whatever the wording is) you will NOT get a defect.  I've done it several times with no defects.  If you do, you can contact ebay to have it removed.  It states very clearly in ebay policy that defects do no occur if buyer changed mind.

I've read on these boards that a defect can occur if there has not been an email exchange between the seller and buyer.  In your case you clearly have, so you should be fine.