The old saying "garbage in, garbage out" comes to mind. Getting the KF8 formatting correct is a daunting task for many, if not most. Amazon is not as forgiving with KF8 as others are with the ePub format. If HTML5 and CSS3 broke every time a web page had a syntax error or some other minor booboo then the internet would look horrible. But web browsers are very forgiving and render our booboos into something pleasing. Amazon chooses to force more perfect formatting though.

My suggestion is to bury your penguin beak/nose in the KF8 documentation until you can create good KF8. Don't use crap like calibre to create a KF8. Don't simply try to convert someone else's garbage. Don't use Sigil to create an ePub then try to convert it. LEARN to do it RIGHT and from scratch.

If it still looks like garbage then you might have a legitimate complaint.