Hi Jayapal,
The documentation for latest version for AEM 5.6.1 for communities package 1.4 mentions that you should use the AEM 6.0 communities documentation instead of 5.6.1. In other words
this section http://docs.adobe.com/docs/en/cq/5-6-1/developing/DevelopingWithSocialCommunities.html#Social%20Communities%20Version%201.4
refers to this page http://docs.adobe.com/docs/en/aem/6-0/develop/social-communities.html
There is a page with basic information about components for developers, including links to the APIs.
http://docs.adobe.com/docs/en/aem/6-0/develop/social-communities/essentials/comments.html
If you go to the APIs, http://docs.adobe.com/docs/en/aem/6-0/develop/ref/javadoc/index.html, and select Deprecated, you will see
com.adobe.cq.social.commons.Comment
@since AEM 6.0. Use CommentOperations and Comment instead.
com.adobe.cq.social.commons.CommentSystem
@since AEM 6.0. Use CommentOperations and CommentCollection instead.
Just to be clear, AEM/CQ 5.6.1 shipped with communities package 1.3 and is documented in the 5.6.1 doc tree.
If you install communities package 1.4 on AEM 5.6.1, the communities functionality is documented in the 6.0 doc tree.
Hope this helps.
-JK