Much like you can currently “Like” status updates, wall posts and other items in the News Feed, Facebook has started rolling out a “Like” button for comments. The feature is not yet live for everyone.
The functionality is much the same as traditional “Likes.” In a blog post, Facebook writes that, “when you click ‘Like’ on a comment the commenter will receive a notification. Other people who can see the comment based on its privacy setting also will be able to see who has liked the comment.”
