Interesting idea to store github comments inside git, the article just isn't very clear to me on how to actually do it.
He's talking about using an "internal CLI tool" so I guess it's not a public tool?
But anyways, this kinda sounds like something you could do though a Github Action right? Like if a PR is merged, run an action that also appends PR comments or other meta-data from github into git
If it's a public repo, revoke the key (on your own/company repo it might not matter so much)
Then
git reset head~1
git push - f