As a Canvas observer and busy parent with already too many things to stay on top of I want the teacher's comments included in observer's Daily and Weekly email notification so that I can see the teacher's comment and can determine if I need to take an action in response. 

There's a huge difference between a teacher responding "Great job!" and "This was submitted incorrectly and can't be graded.  Please correct and re-submit before tomorrow."  The current implementation includes only the fact that a comment was made and a link to open the assignment.  Following this link requires signing in to Canvas, which is often too high a barrier when trying to quickly catching up on a mountain of emails.   The desired change is to include the comment in the body of the email notification.  An alternate approach could be to include a snippet of the comment, which would typically also be sufficient to determine if further action is needed.