Special endpoints
Sitefinity exposes the following special endpoint:
Comments
Comments are exposed as complex property to content types which supports comments.
    - To query comments, create a 
GET request to the following endpoint: api/default/newsitems(<news_id>)/Comments 
    - To post comments, create a 
POST request to the following endpoint: api/default/newsitems(<news_id>)/postcomment, In the request body, enter the comment in JSON format, as in this example: