I think this is especially relevant in this case because this customer spent so much time and effort giving bad reviews that it seems like they must have genuin

I think this is especially relevant in this case because this customer spent so much time and effort giving bad reviews that it seems like they must have genuinely felt that they had been screwed over, rather than being someone trying one on like your example of people returning a brick for a refund. Depending how you/they value their time, they probably spent more than that $4.99 posting those reviews. (Certainly, there are times when I would happily have spent $20 of my own money if meant $5 got taken from some business I felt had treated me badly.)