This is honestly my biggest issue with HN as well. The community has a tendency to downvote well-reasoned, substantive posts simply to express disagreement. I think this is poisonous behavior that will eventually turn HN into yet another echo chamber if left unchecked.

I think downvotes should be removed entirely. Either flag a post for being off-topic, inappropriate or adding nothing of substance to the discussion, or reply with a counter argument to express disagreement to well-written posts that deserve it. The ability to silence opinions different to your own with minimal effort can only hurt the quality of discussion here, in my opinion.