I agree that there should be a way to override this. A possible work around would be to create an Announcement Module where you can create announcements as assignments, give them due dates. In addition, if you wanted to know that your students saw it, you could set up the module settings to require students to mark as complete.
While I will not take the time to send in a suggestion to Canvas about the override feature, I will put a couple here in case someone wants to run with it.
Option 1
1. Toggle feature that essentially says, "Turn off account notifications that are not marked as urgent/critical."
2. Do not allow students to turn off notifications marked as urgent/critical since they are necessary for successful completion of a part of the course.
3. Teacher would have the ability to mark announcements as urgent/critical, so that it would get to everyone. In order to ensure that it is critical, maybe Canvas can require that the announcement is somehow linked to an objective aspect within the course (syllabus, calendar item, assignment, etc.).
Option 1 would be the ideal in my mind especially since the teacher can functionally bypass a student turning off Canvas notifications already by emailing the whole class directly (though that takes a lot of extra time). The student would have to set up an email rule to prevent seeing the email. Since Canvas notifications go to email anyway, under option 1, if a student really doesn't want to get notifications at all whether critical or not, he can set up an email rule to functionally have the same current feature of turning off all Canvas notifications. The question is, should life be harder for the teacher or the student when it comes to announcement settings? Should the teacher have to take the extra time to get into his email, find the email addresses for his whole class, and send an email, or should the student have to take the extra time to avoid getting critical announcements in his email. If a student is willing to pay money to take on the obligations of a course, than it follows to me that one of the obligations would be to receive all critical course content. If a student does not want what he is paying for, it should be harder for him. The work should be on him to avoid getting what he is paying for, not the teacher.
Option 2
1. Toggle feature that essentially says, "Turn off account notifications that are not marked as urgent/critical."
2. Add another toggle feature that says, "Turn off account notifications that are marked as urgent/critical. Note: You will still be held responsible for any urgent or critical course content that is sent through announcements. You can still see announcements under the Announcements tab in Canvas even though you will not be notified of the announcement."
If option 1 is not preferred for some reason, option 2 will at least make clear that the student is responsible for any critical information that they choose not to get notified about.
