So, you say the JBC in direct sunlight was so bright that it burns your eyes and so you have to dress sunlight even to read paper and Kindle.
I too read sometime paper (especially when pages have white background) with sunglasses when I am on beach, for example.
But paper has a far more reflective surface that Triton eink. So I have no trouble in reading JBC with direct sunlight because it has in reality a filter over it.
It is very strange that you said so because your photo seems to confirm my experience:
