I oversee the epub production for an academic publisher, and the epub conversions are created by our typesetter at the end of production. They do indeed do a bi

I oversee the epub production for an academic publisher, and the epub conversions are created by our typesetter at the end of production. They do indeed do a bit of custom programming (and sometimes manual labor) to make the files come out decent. They're supposed to run epubcheck on every file before delivery. I'm the guy who ends up fixing all those little random errors, so I have to insist that the code be reasonably clean and orderly (they work to a spec document that I prepared). Plus, accessibility is a concern. Poorly coded and disorganized files don't play well for people who need assistive reading systems.