>>tonmoy+(OP)
There's really one thing missing from the guidelines IMO - "don't downvote for disagreement, downvote for offtopic/flamebait/inappropriate comment".
Well, this should be obvious, but it sadly isn't...
>>tptace+DO
I've touched on this in another thread under this comment - basically, I think that it doesn't help with the "optimise for curiosity" aspect of the site. Downvoting comments solely based on disagreeing discourages people from posting insightful yet unpopular comments, which is a net negative for curiosity here.