Obviously, you can buy comments too. From "random users" or, better, "other bloggers" which will later promote the same product and confirm its usefulness.
That sort of astroturfing is quite common.
It's all part of the marketing campaign: paid promotional blogs, paid astroturfing comments, buying fake views and likes etc.
They see nothing wrong with this, indeed it seems to be an accepted part of the marketing playbook these days.
Heck I have even busted Batteroo creating an anonymous account on this forum so we know they do this.
Of course they will never engage with nor allow a credible independent blog like mine unless they really believed in their product and claims. Those people can't be controlled so are to be avoided at all costs.
In December though they tried to hire me as an independent tester, which would of course, if I entertained the notion, had me under contract with various clauses no doubt. That failed