A recent change made to the Google Play Policy guidelines and practices forbids the inclusion of  any user testimonials, or direct quotes, in Google Play Store App descriptions (see hereunder "Unrelated keywords or references").
According to the update, it is prohibited to "include user testimonials in your app description. They tend to be dubious and are frequently utilized to include references to popular search terms and competitor apps in violation of the policies outlined here. Let your users speak for themselves via Play's comment review system."
This update reflects Google's strict approach to prevent app developers from adding special keywords to their listing, in order to manipulate the app's ranking by utilizing the users' testimonials (e.g. "Jimmy: So much fun. Like 'Bejeweled Blitz' but with option to collect and free bejeweled!").