The existence of a consensus opinion isn’t an argument from authority. To claim so is an interesting form of the post hoc ergo propter hoc fallacy ('after this, therefore because of this'). The argument for agreeing with the consensus isn’t the existence of the consensus, but rather the same argument that caused the consensus to exist, the underlying body of research.
Framing it as a result that flies in the face of consensus is fun and exciting, especially since people who are science-literate know that a single compelling result can overturn a consensus formed by a large body of previous work. But framing it in that sense is unhelpful, since the vast majority of publications that “fly in the face of consensus” do not. It’s a lot less exciting to view this as one more paper on a large pile supporting MOND, that is still small in comparison to the pile that support dark matter. The paper is obviously worthy of attention and isn’t being dismissed out of hand, it is published in The Astrophysical Journal. But would Hacker News be discussing it if not for the contrarianism embodied by the former framing, as opposed to the latter?
"Here is why the consensus is _______" is not argument by authority, correct.
"The ________ theory/hypothesis is fringe, the consensus is ________" is argument by authority.
See the difference? Phrasing matters in this case. All too often it is phrased the second way. I don't expect someone to literally enumerate all the evidence for or against something, but there is a middle ground between that and just saying "well consensus is ______".
>The existence of a consensus opinion isn’t an argument from authority.
That's exactly what it is. The rest of your argument boils down to, "if a lot of prominent people in a field believe something, it must be because there is a lot of merit-based evidence". That assertion is completely false. Merit-based evidence is one of the ingredients that lead to consensus, but hardly the only one.
I see your point, but I think the person you're responding to is trying to say that he is not saying "if a lot of prominent people believe something then it must be because there's a lot of evidence" but rather "there is a lot of evidence, that is why so many people believe it." The difference there is in actually being able to show you the evidence rather than just telling you to trust a priesthood. I don't think that the person you're responding to is using the consensus in place of the evidence, but rather telling you that if you look into it deeply you'll realize why the consensus exists.
Framing it as a result that flies in the face of consensus is fun and exciting, especially since people who are science-literate know that a single compelling result can overturn a consensus formed by a large body of previous work. But framing it in that sense is unhelpful, since the vast majority of publications that “fly in the face of consensus” do not. It’s a lot less exciting to view this as one more paper on a large pile supporting MOND, that is still small in comparison to the pile that support dark matter. The paper is obviously worthy of attention and isn’t being dismissed out of hand, it is published in The Astrophysical Journal. But would Hacker News be discussing it if not for the contrarianism embodied by the former framing, as opposed to the latter?