Of course. If I am one of your competitors, I can easily decide that all your 1-star reviews are more relevant than your 5-star reviews. I can also convince my FB group of people who share likes of the same thing.
Dark side of things aside, no. It is not possible for people to decide if a review is helpful. I do read Amazon reviews on products before I buy them. However, Fiverr doesn’t seem to be able to understand that most things for sale here aren’t tangible. In this case, reviews ae almost always subjective.
Lol. Fiverr has clearly forgotten how well it worked out when they replaced likes with upvotes and down votes on the forum. How long did that last, 12-hours?