You may laugh but I am serious. Language has moved on and it has been moving on for as long as there has been recorded history.
With HTML5 you get the extra markup for 'section', 'article', 'aside' and there are other semantic elements that already exist - 'em' is not the same as 'i', it infers emphasis rather than making the letters italic.
See the elements as punctuation. Yep, that means writing 'p' tags around sentences. An IDE autocompletes the tags but it is gentle about spelling mistakes and grammar is unknown to it.
You can fully typeset a book in HTML, if you want to comment bits out then you can. With an IDE you can close sections between tags up.
Then there is good old version control. Compare your changes.
The medium has other creative opportunities. I might not finish my book that starts out with 'In 2019 we should be...' until 2021. I could just code that in so the year is correct.
So long as you have some fluency in HTML5 and know the tag vocabulary then the markup in the original document does no harm. Screenplays and plenty of other written forms have a format, tidy HTML5 is now mine.
The semantic tags and the 'outline friendly' structure also help writing. No longer does text just have to be text.
We are so used to 'div soup' style HTML churned out by a machine that we have forgotten what real HTML5 looks like. There is no need for the div, span and other coder-only elements, there is also no need for classes and ids if writing actual content in neat HTML5. With CSS Grid one's copy can be styled with a few basic rules on 'section', 'aside', 'figure' and other top level elements.
Proof reading is pretty good too - refresh the page in the browser. Plus, in text nowadays one does need to cite sources. Links are easy in HTML5, not so easy in other things.
Try it, you will be surprised. Plus, if you should be coding and you are working on your novel, most people will just see a programmer IDE on screen...