I don't remember if I looked at the kindle book in the editor but I had one that I converted to epub and it had a span around
every word. I also think you can get more stuff added depending on things you've set in the calibre conversion settings, so you might try tweaking those if the extra stuff really bothers you.
In my case I think most if not all of that extra stuff is in the css file. I recently tweaked my conversion settings and now a bunch of the css classes have added to them
Code:
border-bottom-color: currentColor;
border-bottom-style: none;
border-bottom-width: 0;
border-left-color: currentColor;
border-left-style: none;
border-left-width: 0;
border-right-color: currentColor;
border-right-style: none;
border-right-width: 0;
border-top-color: currentColor;
border-top-style: none;
border-top-width: 0;
I just ignore it.