One thing that bothers me about the CommentAPI is that the only response you get is the HTTP status code.
HTTP/1.1 200 OK
However, there are cases where it would be helpful to return more information. For example, when I post a comment on a blog that moderates its comment, the blog should note in the response that comments are moderated, allowing the application to notify the user as such.
Otherwise I might assume that maybe there was a problem in posting the comment and then use the web form within the blog itself to repost the comment, only to discover that comments are moderated.