Commenting is possible on any WordPress site via WordPress default commenting functionality or by installing a third party plugin. However, WordPress default commenting lacks some important features that tend to increase user interaction. There are also plugins that help increase user engagement and usability for your commenters. Here, we have listed some of the best free WordPress comment moderation plugins for your WordPress blogs.
Let us know in the comments what your favorite comment-related WP plugins are, whether they made the list or not! You are most welcome to suggest any additions to this list. You can use the comments box below to make any suggestions. You may want to take a look at the following related articles: Awesome Free WordPress Widgets for Icons, Financial Advisor WordPress Premium Themes, Free WordPress Survey Form Plugins and Free Threaded Comments WordPress Themes.
Heateor Social Comments
This plugin let you transform the commenting system of your website. You can enable Facebook Comments, Google Plus Comments, Disqus Comments and/or default WordPress comments simultaneously. You have full control over which of these four commenting systems you want to enable. You can choose between stacked and tabbed interface with re-ordering of the comments.

Akismet
Akismet checks your comments against the Akismet Web service to see if they look like spam or not and lets you review the spam it catches under your blog’s “Comments” admin screen. Automatically checks all comments and filters out the ones that look like spam. Each comment has a status history, so you can easily see which comments were caught or cleared by Akismet and which were spammed or unspammed by a moderator. URLs are shown in the comment body to reveal hidden or misleading links. Moderators can see the number of approved comments for each user.

Show Parent Comment
When moderating comments in the WordPress Admin area, it is useful to be able to see the parent comment if one exists. You don’t need to do anything. Simply activate it and the parent comment will appear for comments that have one.

WP Referrer Spam Blacklist
Plugin in background redirects referral spammer to blank page ( about:blank ). Redirect link can be altered via filter wp_referralblock_redirect_uri. Referrer spam (also known as log spam or referrer bombing) is a kind of spamdexing (spamming aimed at search engines). The technique involves making repeated web site requests using a fake referer URL to the site the spammer wishes to advertise. Sites that publish their access logs, including referer statistics, will then inadvertently link back to the spammer’s site.

Comment Moderation E-mail only to Author
This plugin could also have been called Don’t bother the Site Administrator with every other author’s Comment Moderation Notifications, unless the author has no moderation rights but since that’s a slightly longer title, I chose to keep it as simple as I could. For many blogs or sites where the owner is the only author and his/her account uses the same e-mail address as the Administrative moderator e-mail address, this will boil down to one message to one address.

Gmail Comment Approval
This plugin incorporates the Gmail action API for WordPress comment approval. You can directly approve the comments from your Gmail inbox without logging into your site.
