Update: subscribing is disabled for technical reasons. We hope to offer the service in the next version.
You can subscribe to discussions that you start or join. After you subscribe, you’ll receive an email notification whenever anyone replies to the topic.
To subscribe automatically to any discussion topic you start or join, visit your account settings page and find the auto-subscribe checkbox. Be sure to save your changes by clicking the Submit button.
To subscribe only to particular topics you start, look for the subscription checkbox on when you create a new topic.
See also Unsubscribing from a discussion topic.