>But I know from experience that trying to read a text with long run-on sentences or with obnoxious grammatical features (like an overuse of subordinate clauses) can feel like pure suffering.
It seems to me that until the 20th century, this was considered the "fashionable" and proper way to write. Most of the intellectuals of the time seemed to write this way. I wonder why?
B.R. Myers had a theory on that (in A Reader's Manifesto, not The Cleanest Race): a less literate people are more fond of word games. The common people like to be awed by a skill they don't have; the elites, who can read, like to show off their ability to read and write. Thus flowery prose before mass education, and again at present.
However, I'm not sure if this is true or not; I'd have to look at how many copies of various books sold in the 19th century US, which was not known for its mass illiteracy. Knowing that the Ku Klux Klan got their burning crosses from Sir Walter Scott, I'm suspecting that Myers' theory isn't as comprehensive as it looks; Scott, at least, enjoyed a mass market. (And then there's the steamers from London greeted with the question, "How is Little Nell?")
The real dynamic might be elitism -- a desire to be reading text that the populace wouldn't understand, if they encountered it. That would explain why academic prose has gotten more opaque over time, regardless of what popular fiction is doing -- and would explain why postmodern floweriness is mostly confined to the sort of books that get reviewed in the New Yorker, the New York Times, and the like.
Writing from the 19th century United States tends to be relatively complex, but grammatically so, rather than the sort of existentialist run-on nonsense with which we're latterly so often abused. Here, as a reasonably representative example, is the first paragraph of The Last of the Mohicans [1]:
> It was a feature peculiar to the colonial wars of North America, that the toils and dangers of the wilderness were to be encountered before the adverse hosts could meet. A wide and apparently an impervious boundary of forests severed the possessions of the hostile provinces of France and England. The hardy colonist, and the trained European who fought at his side, frequently expended months in struggling against the rapids of the streams, or in effecting the rugged passes of the mountains, in quest of an opportunity to exhibit their courage in a more martial conflict. But, emulating the patience and self-denial of the practiced native warriors, they learned to overcome every difficulty; and it would seem that, in time, there was no recess of the woods so dark, nor any secret place so lovely, that it might claim exemption from the inroads of those who had pledged their blood to satiate their vengeance, or to uphold the cold and selfish policy of the distant monarchs of Europe.
This was an extremely popular novel in its day, in the literal sense of "popular" - by no means was it read exclusively among the elite, and indeed the literary elite of the time tended to regard it despite occasional equivocation as generally of good quality - although Twain, with his usual inimitable style, quite rightly suggests [2] that Fenimore's work in general should have been considerably less well regarded than it was. Nonetheless, that it was so regarded, and so widely read, can hardly be brought into question.
Well, some think it was to show off their writing. Personally, I think it was feature of a more oral age, because run-on sentences and otherwise odd gramatical structure are way more tolerable when read out loud.
And if you're dictating to a scribe, or writing something which is intended to be a long spoken exposition of some subject (like a sermon or a lecture), then it's less likely that you'll pick on how odd they seem when read. More even, if the majority of readers does read things out loud (which might have been the case) then it won't seem as strange to them too.
It seems to me that until the 20th century, this was considered the "fashionable" and proper way to write. Most of the intellectuals of the time seemed to write this way. I wonder why?