No, thanks.
People would be afraid to express their opinion because the downvotes, just like on Reddit, where new members asking stuff or sharing opinions can get downvoted for no reason, destroying their account with negative votes (banning them automatically from some subreddits, like FFXIV one).
People will abuse it no matter what you talk about.
Upvotes are good enough, you can compare OP's upvotes with other users upvotes on the same thread to check people's preferences. It's healthier.