I realize that out of the box, you can not do this, but Is there a plugin available that enables you to truncate the size of the comments in email notifications?
Example:
Internal employee gives public update: "We have restarted the AMXWEB01 server. It is back up and running. "
The email notification we want to provide is : "We have restarted.... "
The customer would get a preview only for the update and would have to log into the system to see the full public comment.