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I like this thought but note that it would no longer technically be a DAG if you allowed editing earlier comments to link to later comments.

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This is easy to solve by representing edits as amendments. Each edit forms a new "reply" node in the graph with the amended content.

Ooh, interesting - so it's clear that the B responded to A, not to A'. And your DAG ends up A'->B->A (where -> means responds to).

OTOH I'm not sure that cycles are even a huge problem.

They probably aren't a problem, but they might be. I can see there potentially being some graph theory optimisations on the server side you can do if you know you're dealing with a DAG.

> And your DAG ends up A'->B->A

A' would be in response to A.

Or each edit forms a new "edit" node that new replies are then connected to. Regardless, the DAG can always be preserved somehow.

You could edit a comment to violate the DAG criterion, but not every edit that references a prior node must result in violation of the DAG. Those edits which would result in a violation should be prohibited.

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