Reviewboard currently support 3 types of comments: Diff commment, File attachment comments, Screenshot comments.

This is a new type of comments: General comments.
A general comment on a review request is used when a comment is not tied to specific lines of code or a special file attachment, and an issue is opened. Examples include suggestions for testing or pointing out errors in the change description.
The general comment model is built. (review request 6375)

This review request is for general comments web-api.

Add 106 tests for general comments in reviewboard/webapi/tests and all tests passed.