Another feature: let me bang on the downvote or upvote button multiple times to tell the system how much I like or dislike something. Show me more or less or none at all of that topic/user/etc based on that.
Finally and perhaps most importantly, I'd like to see comments and topics sorted by how much my own personal network of influencers rated them. I don't care that 100,000 idiots liked American Idol. I care how much the 100 people I followed hated it (so don't show it to me, ever).
Some people don't like my idea because they say it will create an echo chamber. To them I say that it more closely models real life. In real life, I generally don't hang around with people who I disagree with all the time. My ideal system would insulate people from me if they disagree with me and me from them. Twitter must have a different goal.