And this is why the practice of putting single words into italics for emphasis (again the Victorians are guilty) is so vulgar; a well-constructed sentence should be able to carry a stress on any of its words and should show in itself how these stresses are to be compounded. Both in prose and poetry, it is the impression that implications of this sort have been handled with more judgment than you yourself realise, that with this language as text innumerable further meanings, which you do not know, could be deduced, that forces you to feel respect for a style.-- William Empson, Seven Types of Ambiguity, p. 28.
... We might concede his point for poetry, but does it really carry over to prose? Note that what Empson asserts is that level emphasis is what "forces respect" because it implies that the text has more meanings than we realize, perhaps than we can realize. (Oops, see, there I go.)
Polysemy would not seem to me to be indispensable for respecting a work's style. It rather seems to assume the desirability of a "stylistic sublime," which is corroborated in some degree by Empson's saying that polysemy "forces respect"; force and respect are elements of the sublime. But we can admire a style that is clear and unambiguous, at least for some purposes.
Note Empson's definition of poetry:
... two statements are made as if they were connected, and the reader is forced to consider their relations for himself. The reason why these facts should have been selected for a poem is left for him to invent; he will invent a variety of reasons and order them in his own mind. This, I think, is the essential fact about the poetical use of language.(P. 25; emphasis, of course, added.) In other words, parataxis is the essence of poetry.
That is the exact opposite of what rhetorical prose seeks to do: it wants the reader to carry away exactly one meaning and thus to be persuaded in the manner the author intends. Naturally, TBA thinks of lawyers' briefs. Courts do, to their sorrow, occasionally confront briefs of which they are "forced to consider their relations" and to "order them in their own mind," but they are not typically pleased to be put to the labor, and it does not bode well for the poetical brief writer's chances of success.
And in briefs, certainly, TBA frequently resorts to italics (I try to reserve boldface for blockquotes). A poet may owe his reader the respect of supposing that said reader is unreservedly literate, educated, attentive to nuance, and replete with free time. These are not assumptions I would make about judicial clerks and their supervising judges, and I daresay those readers would not want me to make that assumption. If well-placed italics can help them avoid wondering what the main point is supposed to be, then bring 'em on.