One of the major design decisions was to have no downvotes, which was justified as a way to created "civilized discourse", the idea being that people should discuss their disagreements, resulting in "civilized discourse".

I predicted this wouldn't work because people sometimes have a very strong desire to express displeasure, and if they can't do it by downvoting, they'll do it by writing nasty comments. You don't even have to have used the internet to guess this, e.g.,