Wow, that seems crazy. I can only hope I never have to work with somebody who thinks it is productive to leave that many comments on a change -- I genuinely cannot imagine any change that could ever require that.
Great article, fully agree with all the points.
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.