Discuss: You shouldn’t be able to downvote someone else’s content on a community moderated site without also having to explain why.
A downvote without explanation may deal with trolls but it does a terrible job of encouraging newcomers to a community who just get something slightly wrong. It basically sends the message “f* off” with no explanation or clear path on how they can engage better in the future.
For this reason, it also encourages groupthink not discussion. Anyone who’s opinion differs slightly from the prevailing opinion is down voted. The downvote offers no chance to engage in discussion to explore the issue; it simply says “You’re wrong – end of”.
Basically, a downvote without comment is a door slammed in someone’s face which offers them no path to discuss the issue more, no path to further learning and no path to re-engage with the community. The person who gets it is shut out, and the person who does it just reinforces their own views and reinforces the groupthink of the community.
Of course, it’s not all bad. Some people are just trolls who need many doors slammed in their faces and also communities need a bit of cohesion to survive. But it seems to be an unchallenged assumption that community moderated sites should allow members with a high score to downvote freely, and I think it should be considered more carefully.