I understand that this is the intended policy on HN, but I have seen far too many cases where a greyed out/downvoted comment has obviously been downvoted for di

I understand that this is the intended policy on HN, but I have seen far too many cases where a greyed out/downvoted comment has obviously been downvoted for disagreement to believe that the policy holds in practice. Maybe there should be an 'are you sure?' prompt on pressing the downvote button reminding users of the policy.