If I expect or hope the contributor to become a long-term collaborator, I will submit the comments and wait for them to fix it. I'd rather they learn
If I don't expect them to stay around, I'll make the changes, force-push to their branch keeping their authorship, submit the comments, and let them know what I did and link to the diff caused by just the force push. I'll then ask them if it's OK and let the PR sit for a few days or until they respond, then I'll merge it.
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The more of your expectations you can automate or at least document (e.g. in CONTRIBUTING.md) the easier it is.