If you are talking about high temp silicone, rmb, then I totally agree!
I have been experiencing an awful rattle and today I finally got around to fixing it! In fact, I was going to make my first post about it when I found this one!
The biggest culprit for my 2004 was the inner bezel of the headlight. After swapping my handlebars earlier today, I went for a little spin around my neighborhood without my helmet (which I recommend doing responsibly to find noises) and the sound was awful.
I pulled apart my headlight for the first time by removing the two screws on the side. The inner bezel is held on by 3 metal clips that can become bent and loose. Once I got it out, I applied a thin layer of high temp silicone. If you decide to do this, make sure you to use your applicator tip to spread it evenly.
I haven't had a chance to go for another test ride, but I am confident that it will be better. The assembly seems a lot more solid now and the bezel sits snug. If you have trouble getting the last clip on, I had a lot of luck feeding some 26g wire under the clip and pulling it up to secure.
One other thing that I will mention, is that the engine sounds can reverberate more intensely if your gas tank is empty. I've never heard anyone else's 919 in person, but the engine (especially before it has been warmed up) has been described as sounding like a sewing machine. Correct me if I'm wrong, but I think it's pretty accurate.
Ninja edit: It DEFINITELY sounds like the headlight in your video