From the perspective of someone mid code review during the outage, it's worked as well as it could too. They preserve comment drafts client side that haven't posted to the server yet across page reloads. While it's a little frustrating to have to submit something 3-5x, they're definitely doing something for this use case already.

Also as others pointed out, just because the GitHub app is down doesn't always mean the GitHub git server itself is down.