Google Project Hosting is all about helping software developers work together on source code, code reviews, issues, and wiki pages for technical documentation. When a comment is made, Google send emails to let the appropriate users know when an issue has been entered or a comment has been added to an issue, wiki page, or code review. These emails contain a link that allows you to enter your response in your project on code.google.com/p. But now, it's easier to respond to these comments;
just check your inbox for new notification emails, when you see an email footer line that says that you can reply, just press the reply button in your email client, bang out a thoughtful response, and hit "Send". Project committers and owners can even update an issue's status and other values via email.
For e.g., to let your teammates know that you're working on an urgent defect report that just came in, reply with: