>>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...
>>Pannon+Ch
Not only is it not in the guidelines, the opposite principle is part of HN jurisprudence: downvoting for disagreement is explicitly approved here, and has been since Graham. The idea is that those downvotes are more succinct and produce a better conversation than the rote disagreement comments would be otherwise.