Facebook officially rolled out the ability for users to respond to comments via email, which it began testing with a small number of users last month, Facebook News Feed team engineer Tom Whitnah posted on the Facebook Blog.
As long as users’ Account Settings permit them to receive email updates from the social-networking site, they can reply via email to comments on Facebook content such as status updates, photos, videos and Wall posts.
Today, we’re launching the ability for you to participate in these conversations by replying directly to these email notifications. When you receive an email notification about comments, you can just click “Reply” and start typing a comment at the top of the email. Then hit “Send” from your email and your reply will automatically be added as a comment on Facebook without you having to even log in.