Read this on one of the boards I follow. Seems over the past week comments on some apps would disappear and later reappear. This has been going on over the past week, and a bug has been reported so odds are Apple will fix this soon. So if your wonder what the heck happened to your comments? Give it a bit. It should come back and I’m sure Apple will sort it out pretty soon.
If anything new comes up I’ll update this post.