You may have noticed the helpfulness rating on guides.
In most cases, this provides a reasonably realistic reflection of the worth of a guide, but as with most things it can be abused.
Guide writers can enhance the reputation of their guides by positive votes from friends and depress the rating of their rivals by using the "not helpful" button.
Since the identity of the "reviewer" is not made available to the person who has written the guide, or the reason for a negative review is not offered, there is no way of checking. And Ebay will not provide this information, although reviewers have to log in to review.
As Guide (& Review) writers provide this service for free and may have taken a lot of time & thought to prepare their Guides, it can be annoying to receive negative reviews without knowing who or why.
I have suggested to Ebay that the negative button should be removed and just postive feedback should be given. Obviously this is still open to abuse, but it removes the possibility of anonymous vindictiveness by some reviewers.
Maybe you've got a better suggestion. Tell Ebay. They may listen to you.