In order to be notified when an employee adds an internal comment to a CMS page, you'll want to walk through the following steps:
Navigate to the Operations Portal
Go to the Notifications screen
Look for the checkbox labeled "Notify me when an employee creates an internal comment on a content page". Then check the box to enable the notifications.
Once enabled, you will receive notifications whenever an employee adds an internal comment to a page. Here is an example of what that email notification will look like: