Earlier quoted context omitted.
Acting out in retributive ways when your customers (justifiably or not) have issues and leave negative reviews is a pretty terrible way to build and run a business. Is the spite towards that one person really worth it?
Look at the timing. This was an Amazon purchase. The developer mentions Saturday, and how the Amazon review was left around the same time as the forum post, so presumably the the item was delivered on that same day. That's gonna be a bad experience for both sides: The purchaser has to wait until Monday to return, and the developer has to deal with (what I expect is) a drive-by flame. It's a Saturday night, and each s…
You work out what their problem was and fix it, if they explain the issue. Regardless the attitude should be "how do we make sure the next buyer doesn't have an issue".
You are going to get bad reviews no matter what, some entirely unfair. All you can do it focus on making the product as good as it can be.