Isn't this against their terms of service?
Obviously, nobody would want to allow fake reviews on their site and degrade quality.
I have been selling on Fiverr for almost 1.5 years now, and I started with Fiverr Reviews to my first gigs and I got my first sales from that.
I havent been banned so far, if you abuse the reviews you will probably get banned now if you get one or another you should be fine.