If you see a commented indented underneath another, that's site's way of telling you it's a response :). For messages that are posted in reply but are shown far down (like this one), you can put your cursor on the middle of the avatar - or the box where the avatar would be- scroll up untill you reach the edge of an avatar, and that's the one that it was replying to. Eventually you'll get a trained eye for it, but that helps untill then :)
