Meanwhile, YouTube has gone and changed the video codec, further degrading the quality of the Hand Test II video and undoing all the work I put into reducing the banding. 
Since they retain the original uploads for re-encoding when better codecs come along, this means all I’ve done is permanently degrade the original myself by adding copious amounts of noise to it.
Twitter completely butchered the one I uploaded there (and I couldn’t preview it before posting, since they’ve removed that functionality 
), so instead of trying to tailor videos to encoders on specific platforms and sabotaging them in the process, I now recommend uploading in the highest quality possible and let them take care of the sabotaging for you.