Hi @EricMagidson,
Thanks for making that great screencast, it was definitely well done! Personally, I do agree that comments should probably support HTML, but I also can somewhat understand why they don't, as the small comment boxes would struggle to to fix icons above, and I don't think most people would know keyboard shortcuts...
With that being said, we found some very related ideas to this have been submitted: [SpeedGrader] Hyperlinks in Assignment Comments - Instructure Community and [SpeedGrader] Allow HTML in Assignment Comments - Instructure Community. While those are both closely related, they are not exactly the same as your request, since you're working form the grades page and not SpeedGrader. I'd think if either of those ideas were developed, they should apply to all comment areas, but Canvas engineers may not agree, so it's beneficial to have all possible ideas submitted to the Community's ideas area (the more you split your idea into individual components the better). You may not be able to post there right now as a new user, but if you browse around the community a bit and rank up to Community member, you should gain access to make an idea posts pretty quickly. You cold include your video in the new idea post(s) as well as it clearly shows what you're looking for.
I hope this helps a bit, even though I know it's a bit of extra "homework" for you.
-Chris