I've had some PRs that would have required a ton of comments. There are usually two ways I handle this:
If the PR went in a completely different direction and missed the goal by a lot, I take ownership of it (with a brief explanation) and re-implement it. I then use the new PR for a pairing session, where I walk through both PRs with the original author for learning purposes.
If it’s mostly smaller issues, I schedule a half-hour pairing session with the author and review everything together, after preparing a list of issues.
Doing it any other way puts too much burden on the author to guess what the reviewer wants, and it slows down velocity significantly.
If the PR went in a completely different direction and missed the goal by a lot, I take ownership of it (with a brief explanation) and re-implement it. I then use the new PR for a pairing session, where I walk through both PRs with the original author for learning purposes.
If it’s mostly smaller issues, I schedule a half-hour pairing session with the author and review everything together, after preparing a list of issues.
Doing it any other way puts too much burden on the author to guess what the reviewer wants, and it slows down velocity significantly.