Entertaining and thought-provoking paper, as ever, Simon. Makes me miss the days we had such cross-disciplinary conversations more often. It seems to me to be largely an update an continuation of Monastic XML [1], so I'm surprised you didn't reference that in your paper. I guess you were keeping the argument self-contained.
Most importantly thanks for the extended Ruskin quote. I haven't really read Ruskin since I was a teenager, when he influenced me deeply. I should take another round with the original text. What he writes still affects me deeply, and still resounds with my feelings about how industrial-scale commerce has affected the arts (e.g. [2]), which I agree with Ruskin largely derives from the fact that the early industrialists looked to Athens rather than, say Thebes or Lo-Yang for their models.
I do think it's a very tricky analogy to make with markup, though, and I'm not at all convinced that JSON is any sort of oasis from imperial constraints-making or top-down design patterns. But the important thing is that there is always value in re-examining the parallels we draw between computing and the arts.