I think that there are two roads by which text can become art, sketched out below:
The first road by which text can become art is by containing beautiful content. For example, words from the dictionary could be used in a very specific order, with the outcome being a poem, a love letter, or "Ulysses". Here the focus is less on typography and more on the vaguely defined "content" of the text.
The second road by which text can become art is by emphasizing stylistic parameters, a science which I call "Fontplay". As any aspiring "fontplayer" will soon realize, aesthetic perturbations only make sense within an exceedingly limited portion of "content space", and vice-versa. Despite this seeming parity of mutual constraint between content and style, it is the exploration of "style space" that facilitates rapid exploration of "content space", and not the other way around. The implications of this are that the train of thought runs on (or through the country of?) style, not content. Rearranging post-it notes or making concept maps to generate new ideas are two good examples of how syntactic mutational processes can induce directed semantic evolutionary change.
Indeed, the Syntactic (style) road actually encompasses the Semantic (content) road. One only-partially-fallacious reason why this might be the case: all books can ultimately be restyled in a different font, but it doesn't even make sense to ask if a font could be rebooked into a different meaning. Thus books (content) represent only one possible generalization of font (style). Not checkmated yet? Borges's Library of Babel contained an infinity of texts, differing from one another in their symbolic content. So if the set of all possible rearranged books in a certain font set is infinite, shouldn't the set of all possible content-by-font combinations then be transfinite? A closing argument that initially seemed like it might contradict my case, but actually was deemed to support it, is John 1:1.
So perhaps the relationship between Content and Style is less like two parallel roads and more like a bike lane going down the median divider of a communication freeway. The bike traffic (message content) is surrounded on all sides by the car traffic (message style). Despite Newton's Laws, crashes between cars and bikes are usually more painful for the bike rider. In other words, illegible font or off-putting style can destroy the content of a text, but no aberration of content may ever sully an artistic style.