I'm not going to downvote you just because I disagree with you, I'm going to write you a comment about what I think instead :)
I don't consider that appeal to authority canonical. My opinion is that downvotes should be used for bad comments, not for comments you disagree with. These aren't the same thing.
You can't downvote me because my comment was in response to yours. It's not an appeal to authority. It's a statement of fact as also seen in the implementation itself.
It is the definition of an appeal to authority to quote an authority figure as the final word on some debate. I've been here since before that first comment from pg about this, and no, I don't agree that it's a "fact" that this is "how HN has always worked", and no, there is nothing in the implementation that unambiguously makes downvotes be for disagreement.
But again, I'm not arguing for strict rules that work the way I prefer. I'm saying, this is a community I participate in, and I have my own opinions about how best to participate in it, which aren't necessarily aligned with the people who created the site 15 years ago. Other people are entitled to differing opinions about this, and can use the site how they prefer, but I still have my own opinions and will advocate for them.
I don't consider that appeal to authority canonical. My opinion is that downvotes should be used for bad comments, not for comments you disagree with. These aren't the same thing.