Facebook announced changes to its Comment Box widget, now if a site owner implement the Facebook Comments Box widget underneath content on a site, visitors who'e already logged into Facebook can comment without having to log in again.
The new comments box also supports some third-party log-ins. Additionally, if someone who comments keeps the "send to Facebook" box checked, their comment along with a link to the original content -- will appear on their Wall and in their friends' News Feeds.
The new Comment Box is also designed to use social signals to surface the most relevant comments to the top. Facebook has also added more moderation possibilities, allowing admins to adjust the visibility of comments, ban users and blacklist words.
"Discussion threads stay synced across Facebook and on the Comments Box on your site regardless of where the comment was made," Facebook said. "Users will also receive a notification whenever another user replies to their comment. Clicking notification will take the user back to the web page where the comment originated, driving more traffic back to your site."
Web site owners who've a Facebook Page for their sites can comment on a site's content while logged in as the Page admin. Then, Facebook users who've "Liked" the Page will be able to see that comment, and a link to original content, in their News Feeds and on the Page's Wall.
For information to implement it on your site read here.