MBPr 15" - Display Gasket damage suggestions?

I agree! Its not enough to even try! I should add the gasket is just not available as a spare and even finding a salvaged one is just not likely any more.

Here's a good teardown of a retina display its not easy and even the newer Fn & TB displays are not any easier MacBook Pro Retina Display Teardown

If presentation is really important I would recommend getting a large screen iPad, I have an iPad Pro which I show my work (photographer/museum/theater backdrops as well as large lobby photo murals) with a projector.

I’ve done a bit of research and it seems like rubber gasket replacement is a thing but it’s niche and challenging. I haven’t found much info on it or a part; I’d likely leave this to a pro repair shop. My hope is that since the broken off bit is still a good fit and even sort of sticks back on, that there’s a matte/black epoxy or something that’s nimble enough to fill that small seam between the gasket and the broken off part without looking like a tacky diy glue job. In theory this should be very doable but I have poor knowledge in this area

I really don't recommend it! The rubber is silicone rubber so you would need something that adheres to it and is flexible.

After fully cleaning the surfaces and masking it off you could use something like this Sil-Poly adding a black pigment to it.

I’m quite curious to see what others have to say though I appreciate you sharing your perspective and thoughts. The tape off and apply method with a silicone seems pretty interesting given how little is actually needed and how little there is to lose trying. I will do more research and see how cleanly this could be applied with a meticulous hand/small tool, and if there’s a black pigmented silicone. Will update if I go this route