This is Plugins: Content - EasySocial which displays author's information at the specified location of an article. It enhances the article usability by adding EasySocial comment form on the Joomla Articles. This plugin is by default installed on your site, however, in a case whare you unable to locate this plugin, worry less my friend. You can download it from our Apps Store.
Please take note this is a plugin, and it must be installed through Joomla Extension Manager. For more information, please read through Installing Plugin documentation.