We do a lot of post-commit reviews in our project, using the Audit tool.
I wrote a command line wrapper to query commits where I've been marked as an auditor, using arc call-conduit audit.query. Unfortunately while I can query audits and even view the corresponding diffs from the command line, there's no way to actually accept them.
Note that while there is a Differential comment API which is exposed, and for which the accept commit action can be supplied, the API call requires a revision ID and the majority of commits which I'm auditing don't have a revision ID.