Metadata is useful! The problem is that 1D "good/bad" being used to order comments is not a reasonable approach. In a more nuanced system there's less incentive

Metadata is useful! The problem is that 1D "good/bad" being used to order comments is not a reasonable approach. In a more nuanced system there's less incentive (other than wrecking) to inaccurately mark comments as being "informative" or "technical" or "political", because instead of changing global comment visibility you're only changing it for the subset of users who are using that attribute to guide their reading. There are honest differences of opinion as to whether a comment fits in certain categories, but these are more specific and less contentious than "good/bad" and so I'd expect a much better SNR on them. Collapsing threads is nice but the importance of defaults to the user experience is hard to overstate. At each step of an interaction chain more users will fall off and not end up at the goal. Lots of people will never use comment collapsing if they have to manually do it.