In my philosophy 101 course we spent several weeks attempting to define “art” in such a way as to exclude everything that wasn’t art (the lesson there, as you can probably tell, was that there is no universally accepted answer). “Literature” is kind of a funny term because most people do understand how it’s commonly used: creative writing, if not excluding genre fiction then at least meeting some standard of artfulness (not met by most genre fiction, apparently). In book stores where I live in the northeast USA, “literature” sections are full of “culturally significant” stories, while novels that haven’t had as long to sink into the cultural consciousness or left little impact are simply “fiction.” These standards are delineated and enforced by the bookstore workers, not by any philosophical body, which is probably as it should be, since for the vast majority of people (not building syntactical digital systems) understanding the vibe of the word is enough.
In our discussions about art, folks brought up intention: a geologist might not consider their surveying photographs or LIDAR scans art since their purpose is purely utilitarian, but someone else finding them at a garage sale could consider them beautiful and hang them up. It might be the case that an author seeking to write a pulp novel or diary finds themselves lumped into the category of literature without trying.
But regarding Hanon’s point, definitions work insofar as they are useful. Everyone knows what a chair is, but defining the word in such a way as to exclude everything that is not a chair is surprisingly difficult. If you asked 100 people on the street if the text on a stop sign constituted literature, your answer would be clear: not in any meaningful way.
And re: Mathbrush’s comment earlier, an artist could come along with the goal of changing peoples’ minds by imbuing the humble stop sign with meaning. It wouldn’t change the inherent meaning of a stop sign, but it would perhaps alter how we think about them, which is what a definition is supposed to tell us, right?