Annoyed because you have to leave your e-mail inbox every time you would like to respond to someone else's Facebook status update? Good news: the social network is testing a brand new feature that will enable you to comment on threads by e-mail. It appears as if the new feature is currently being tested only with a very small subset of users; we haven't seen it at the bottom of any Facebook notification e-mails yet and there are only about 4 tweets from the past couple of days mentioning the new feature.