This hurts a lot to watch, but I really appreciate the conclusion she draws at the end about showing gratitude for positive impacts even if the experience isn’t great as a whole. A few times I have gotten thank-you emails after a semester that have remained extremely meaningful to me many years later. I wish I could let them know the impact it had, but I’m not going to hunt down old students. I would say don’t feel any need to send something if you don’t fully mean it though, platitudes after a student sees their grade are not the same. They’re not insulting but if it feels like a template the student could send to all their professors with a couple changes it just comes across as networking.