Not sure why this is downvoted, it’s absolutely correct. I tried this myself; it would have -greatly- simplified scraping Word docs because the custom tags would have been available for XPath querying. Alas, Word strips it all on open.
From the paper: "The purpose of writing is to convey ideas to the reader. The purpose of formatting is to make the document easier to read, not to look pretty."
I find that thesis a bit reductive. For technical writing, I can agree - the purpose is to convey ideas. But, there is a whole other class of writing that isn't intended to convey ideas, but _emotion_.
Also from the paper: "The purpose of document design is to display the logical structure of the document through its formatting, thereby making it easier to read."
Again, there's a whole other class of documents whose formatting takes precedence over the logical information, intended to evoke emotion.
Not to take away from Lamport, who is seriously brilliant, but there appears to be a blind spot here.
"I used to hate writing assignments, but now I enjoy them. I realized that the purpose of writing is to inflate weak ideas, obscure poor reasoning, and inhibit clarity. With a litte practice, writing can be an intimidating and impenetrable fog!"