Voting is not the point. The point is to bring to people's attention things they will be interested in. HN/Reddit/etc do this through voting. Twitter does it

Voting is not the point. The point is to bring to people's attention things they will be interested in. HN/Reddit/etc do this through voting. Twitter does it through retweeting, which is similar to how it happens offline. So, it's acceptable because it's part of the medium.