Unless you have changed your settings to stop email notifications, it's likely that you receive an email every time someone comments on your status updates, photos, videos and Wall posts. Before now, the email contained a link that you had to follow, which logged you into Facebook where you could reply. You'll now notice that the email contains a line reading "New Feature: Reply to this email to comment on this link."
Now, the site has made it possible for you to respond to these comments directly, by hitting the reply button. All you have to do is enter your response and hit send, and Facebook will add your comment to the site.
This is big news for all those Facebook junkies out there who can't get their daytime fix while at work because of a company firewall, not to mention all the students who can't check their Facebook for several hours every day. We'll see where productivity levels go after this.
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