Comments can be closed by either the Review Coordinator, or the Reviewer who made the original comment.

If a comment is being closed by a user who did not leave the original comment, then they will be prompted to include a reason for closing the comment as part of the review audit histroy.

Closure Options

Closed

Closing a comment means that it has been addressed and resolved, with the Reviewing party satified with the response provided by the Author.

Closed - Dependent on new revision

Closing the comment dependent on the next revision, means that the Reviewing party is satisfied that the comment will be addressed within the next revision of the document. 
Upon the next revision being uploaded for review, the Reviewers can view the latest and previous document revisions in comparison mode, where any Closed - Dependent on new revision can be reviewed to ensure that they have been addressed.  If they have then the comment can be updated to being fully Closed. 
If the comment has still not been addressed, then the Review Coordinator or the originating Reviewer can forward the comment onto the latest revision to indicate to the Author that it still needs addressing.