There is no consistency. I have a comment at -2 right now. Over the past few days it oscillated between positive and negative scores. Someone replied to it and my response is currently +6.
In those cases its multiple people consistently disliking your posts. This doesn't necessarily make their downvotes any more valid or intelligent, or the post not worth seeing.
None, but downvoting because of a disagreement makes you an asshole, so that still tells you stuff about the community, or at least those active in certain threads.