Yes, there is an option to add comments in the content approval page where an administrator and a user can discuss the campaign. The steps are, Click Show comments in the Campaign Detail View page. This will take you to the approval process page. ...
Administrators get notified via the notification bar when a campaign has been requested for content approval, which they can either approve, hold, or deny.
No. Users who have been marked to go through the content approval process cannot send out campaigns unless the campaign content has been reviewed and approved by an administrator.
No, it is not necessary to use the same subject and campaign content. Feel free to give your chain a new subject line and content, or select the option to clone your content.