People tend to score comments based on who says it as well as what is said. Simple change I think could improve signal-noise ratio: Make username invisible until after an upvote, or disable upvoting after viewing the username.
My favorite commenters/contributors are quite identifiable by their phraseology, wit, and wisdom. And I think the reverse is true. Spending much time here brings a familiarity of who is saying what.<p>And in rereading your expected result, I now realize I don't know how your proposed change would change the signal-to-noise ratio even without the above.