I think the publishers (or maybe the universities? or anybody at the center of a community of experts really) should host an API which maps set of CTPH hashes to URL's (or ideally, CID's for use in something like IPFS). The goal would be that anybody (author or otherwise) could attach metadata after publication.

Maybe it's criticism, maybe it's instructions on how to get the included code to run, maybe it's links to related research that occurred after the initial publication...

Suppose you have metadata to attach, you generate CTPH's for the article, pick a subset of them which corresponds with the location you want to anchor your metadata to, and upload the pair to the context aggregator (these would likely be topic-centered, so if it's a biology paper you'd find a biology aggregator).

When people view the paper, they can generate the same CTPH's and query the appropriate aggregator, and they'll get the annotations back which link locations in the article's text to metadata that, for whatever reason, was not included in the original publication.

I want to use CTPH's instead of DOI's or somesuch because they don't require a third party to index the items for you, and they still work even if you have only part of the article (like maybe the rest is hidden by pagination or a paywall). You could do a speech-to-text transcription, annotate it in this way, and somebody else who generated the same transcript could then find your annotations without ever creating an ID for the speech you're annotating.