I made meticulous comments on my students' work and it disappeared. This is not a case of not clicking submit, I was able to go back and refer to these comments and then all of a sudden they were gone. 

There are literal YEARS worth of comments that this is happening and it seems Instructure isn't doing anything about it, including acknowledging that it's their problem. 

This is a real problem when you're telling students that you've given them full comments and they see nothing - especially when they really love to go up the ladder if they're unhappy with a grade. Canvas has taken a relatively stressful part of faculty life and made it unnecessarily and exponentially more difficult. 

Fix the issue. Be up front with your customers. Know that there are plenty of other LMS out there and that when you hang faculty out to dry because of faulty code and lack of accountability, we will absolutely make it our mission to get our colleges and universities to switch to anyone who isn't Instructure.