Last night, while googling the answer to someone else's Returns-related question, I found this link to Everything I Ever Wanted to Know about eBay Returns. I thought it was interesting because it seems to me to be more comprehensive than the Returns Guide that was released with the 2015 Fall Seller Update and it answers virtually all my questions about how Returns are really supposed to work on ebay.ca and ebay.com.
For example, a few months ago there was a seller who found she had inadvertently accepted a buyer's Returns request simply by answering their Message about it. This link states that is definitely NOT supposed to happen.
And while I am waiting for an ebay.co.uk Returns Request to time-out, and wondered aloud when accepting a Return for reasons of Remorse, whether that meant I was obligated to refund the full purchase price including lost postage when I got the item back. It turns out that I am NOT required to do so in the case of a Remorse Return which makes me question the necessity of a restocking fee but that is an argument for another day. Remorse Return = Purchase price of item only.
Here it is, feast your eyes, bookmark the page like I did: http://pages.ebay.ca/help/sell/return-process.html
Like I said, much of this information is in the other, more attractive and succinct guide but I found this to be better organized and easier to digest. Text heavy but it's all there.