Jonathan in the vein of decorum. Interesting.
Decorum, in one way, seems like a kind of reality principle. Style to fit the subject : but how do we know what fits unless we know something about the subject? (Reminds me what Frost said once: something like - only amateurs try to tell us something we don't know in poems; the pros stay with what everybody knows.) (I've probably mangled that into oblivion. Ne'er so well-express'd & all that.)
But then there's the decorum of style itself, & styles. Fashions quickly build their own boilerplate template collections. This is decorum in the one-way mirror, I guess.