Updating comments not created on GitHub does not create them on GitHub

[joshsmith]

Problem

Steps to reproduce:

• Create a comment on Code Corps that for some reason does not sync to GitHub.
• Update that comment on Code Corps and save.
• The comment does not get created on GitHub.

I'm not sure what the working case should be or how we should handle this generally. It's theoretically possible that we end up in a situation where there are pending operations to GitHub that have not returned yet, and we do not want to overwrite those or create new comments, nor do we want to block our user from doing something as simple as updating a comment.

This probably gets resolved depending on how we decide to rearchitect things in #952.