On StackOverflow reputation is subtracted when downvoting answers but not questions [1], which is a neat approach. On your own profile, you can see the proportion of upvotes to downvotes (as well as other activity), but others cannot (maybe moderators?). So, there is at least some personal impact to having a user be accountable for a downvote. There is also generally a culture of "if you downvote, you should explain why", which sometimes seems to be here on HN as well. I remember Disqus removed the downvote count some time back, and Facebook doesn't have a "Dislike" button, so there are different approaches to it. I wonder what some other approaches some communities have taken, and what would be effective? Or even, what is the desired impact?

[1]: https://meta.stackoverflow.com/questions/251610/why-does-dow...

[2]: https://disqus.com/home/discussion/supportqa/why_was_the_dow...