I think that since it's not possible to reply to multiple comments at the same time, people will naturally open a new top-level comment the moment there's a clearly identifiable groupthink emerging. Quoting one of your earlier comments about this:
>This happens so frequently that I think it must be a product of something hard-wired in the medium *[I mean the medium of the internet forum]
I would say it's only hard-wired in the medium of tree-style comment sections. If HN worked more like linear forums with multi-quote/replies, it might be possible to have multiple back-and-forths of subgroup consensus like this.
(I'm referring to how this comment, objecting to the other comments as unduly negative, has been upvoted to the top of the thread.)
(p.s. this is not a criticism!)