Down-vote comments could be hidden by default so as to not pollute threads too much. I really like the idea of private comments for this case. Wild tangent

Down-vote comments could be hidden by default so as to not pollute threads too much. I really like the idea of private comments for this case. Wild tangents, pedantry, grammar/spelling corrections, personal questions, (constructive) criticism could all be optionally made private and avoid clutter in the threads