A Long time ago...
People used to use H tags for different sized fonts, not for just 'headings'.
Since they really dont matter, and the really don't add significantly to the overall file size... Why is this being
sweated? 99.99% of the book's readers will never even know that is there.
Personally, I dislike the mix of style definitions: CSS, On page (in the <Style>, and in line (style=) a whole lot more.