Not quite sure how reading levels ended up in the comma thread but thought it deserved its own. Here's an interesting article on that subject (https://contently.com/strategist/2015/01/28/this-surprising-reading-level-analysis-will-change-the-way-you-write/). I'm copying some interesting parts here (I'm not bothering with quotes or the < quote so just know everything below this is copied from the article):
Apparently, my man Ernest [Hemingway], the Pulitzer- and Nobel Prize-winning novelist whose work shaped 20th-century fiction, wrote for elementary-schoolers.
The initial surprise from my little data experiment is that writers whose work we regard highly tend to be produce work at a lower reading level than we'd intuit. Cormac McCarthy, Jane Austen, and Hunter S. Thompson join J.K. Rowling in the readability realm of pre-teens. The content of McCarthy's and Thompson's novels isn't meant for children, but these writers' comprehensibility is rather universal.
I did an informal poll of some friends while writing this post. Every one of them told me that they assumed that higher reading level meant better writing. We're trained to think that in school. But data shows the opposite: lower reading level often correlates with commercial popularity and in many cases, how good we think a writer is.
In eras past, sophisticated writers aimed to entertain and persuade a sophisticated audience with big vocabulary and complex ideas. (Case in point: Ben Franklin's autobiography—one of my favorites—is written at a 13th grade level.) In recent years, it seems an increasing number of sophisticated thinkers have intended to reach larger audiences through literary simplification (e.g., Malcolm Gladwell, one of the smartest people I've met, who certainly could write at a 13th grade level but intentionally writes at 8th grade level in order to bring complex ideas to an audience that wouldn't hang at a higher level).