Sculptors working in wood sometimes paint over the wood. Others work with the grain, exploiting any knots or defects. Apparently this "truth to materials" credo goes back to William Morris et al - a reaction to decorative Victorian design and architecture, to mass-produced veneer. Modernism (in the guise of the Bauhaus movement, etc) continued the "honesty of construction" credo. In the 1930s, Henry Moore, argued "that sculpture in stone should honestly look like stone; that to make it look like flesh and blood, hair and dimples is coming down to the level of the stage conjuror". In 1941 he wrote that "[o]ne of the first principles of art so clearly seen in primitive work is truth to material; the artist shows an instinctive understanding of his material, its right use and possibilities" though he later admitted that he'd been too obsessed by the principle.
According to Greenberg in "Towards a Newer Laocoon" all arts in the twentieth century "have been hunted back to their mediums and there have been isolated, concentrated and defined. It is by virtue of its medium that each art is unique and strictly itself. To restore the identity of an art the opacity of its medium must be emphasized". Poetry's medium is language, but oral or written? Though oral poetry came first, the written word has an increasing primacy. The rejection of transparent language leads to a treatment that takes into account the quirks of words (pronunciation for oral poetry, spelling and typography for text) exploited most ruthlessly by "sound poetry", "concrete poetry" and some Oulipo works.
Less extreme approaches show a palimpsestic awareness of the medium without being dominated by it. A poet might be drawn to use a cognitively unexpected word because it rhymes conveniently, or because of alliteration. "rough" and "through" are sight-rhymes - a quirk that one can gloss over or work with. Such awareness of the underlying substrate (be it letters or sounds) is characteristic of one type of poetry that tries to distinguish itself from prose (though not from "Finnegan's Wake"). Heather McHugh and Paul Muldoon are amongst the exponents of this linguistically embedded poetry, poetry for people who can see both the wood and the trees much as some people can appreciate both the sound and the meaning of poetry.