Support for someone responding to a comment

[jeffreysilver]

It would be really helpful to get notified when someone comments on a pull request, or responds to a comment that you authored.

[EnixCoda]

Hi, @jeffreysilver
I may not extend this project's features in the future as GitHub has introduced its official scheduled reminder. It has all features of this project, even the one you are asking about.

But PRs for it are welcomed!

[EnixCoda]

Recently I'm considering optimizing this so that I can use it in GitHub Enterprise, where the official scheduled reminder may not be available. This feature should be included.