There is a very biased one sided truth with only being able to up vote something... does it mean I can't "not" like something? Balance should exist in everything... Down / dislike voting has a strong potential of filtering out really bad comments / threads and noisy trolls as well as re balancing an idea which might gather some up votes but far more down votes (if they existed). You may think of this as democracy... you always have people who are pro and contra. To all those opposed to down voting out of fear of negativity "hive mind"... maybe that hive mind has a point and down voting is a way to express that disagreement. You just can't get a clear picture if you only can promote something and not demote something. Thread votes do not need down votes for the simple fact that a negative idea can ALSO receive up votes... but in-thread replies could certainly use some community moderation and attention. Still not convinced? How is this fair towards people who don't agree?: https://robertsspaceindustries.com/spectrum/community/SC/forum/3/thread/upvote-if-you-are-okay-with-current-mouse-mode