basically the passive-aggressive responses will become the norm, the score of the unfavorable user will drop, and the living man or woman behind the user will feel like shit;

Black Mirror [Season 3 Episode 1] - Nosedive narrates this exact scenario: people rating each other (i cannot remember whether dislikes were present); here is a youtube review of that episode and how it relates to modern life;

the end of the episode is very refreshing!