You need private notes because you will get pull requests that you are not sure about.
You want to post a comment for your colleague
to look at but you don't want the pull requests contributor to see that notes.
GitX allows you to add notes in pull request/issue pages and these are only visible to project collaborators and not any other users.
While building Chatwoot, we got a lot of pull requests.
For each pull request that needed discussion among the maintainers we used zoom, telegram, and a few others.
Then we thought of why not use GitHub for private communication among the internal team. In the end, we build GitX.
Our main goal is to keep all the internal discussions among collaborators in Github itself.