On the Facebook Help Center Page also this update has been made, where facebook stats that,
On a Page post, the name of the person who posted will be listed below the name of your Page next to Posted by. On a Page comment, the name of the person who commented will be listed below the comment next to Commented on by. Keep in mind that only people who help manage your Page can see this information.This will also helps admins to get information about who posted or scheduled posts in your Page's activity log. Facebook also mention that this feature is not available to everyone right now, but soon it will get available.