English has a lot of non-linear structure to it. Not just the syntax tree within each sentence (subject, verb, object, main and subordinate clauses...), but also between sentences (which claim supports which other claim, what sentences are meant to be contrasted with each other, parallelism...) Far from fully formal, but there's a lot there that you absolutely can define standard ways to highlight/indent. I just thought in my head "maybe text inside of quotes should be grey, so it's easier to see that it's a quote - of course that's unviable in typewriter world and cumbersome in pen-and-paper world, but easy today", and then I realized that modern blockquotes work that way already.