I have a couple of 5 book series and lately people have been buying and refunding them in the order in the series. I know it's the same group of people and at first I was POed. But then I realized that even though they don't pay for the books by returning them, my sales rankings go up. And also, to go through the trouble of buying and returning, they must like my writing. Now if only I could get them to leave reviews....
I have a few who do that to me. You can always tell. When you suddenly get refunds on every book you've written within a few days, and you can watch them read and return every book in your series, one after another. Drives me a bit nuts too, but like you, I've found that the temporary sales rank bump helps me sell more books, so it evens out.
On reviews, not really a big fan. I don't read mine because I write erotica and that's a bit like asking someone to grade my sex fantasies.
It looks like that is happening to me. Suddenly someone is going through my list of books and refunding. Some of those titles are books nobody ever buys, so what is happening? Are they reading them fast and asking for a drefundm or copying the downloaded book to another platform and then refunding? Some people are hoarders of books they never read. Who does this stuff?