Comments Notification Customization allows users to toggle comment notification emails (those that are not associated with a comments Email Template) on and off. When toggled on, if a user makes a comment, every other user who has made a comment the commenter will receive a comment notification email.
Comment notification emails are sent to each user’s notification email. See Update Profile for how users can set their notification email.

To turn emails to commenters on:
> Customization > Email Notifications.
To turn emails to commenters off:
> Customization > Email Notifications.