I don't think that's the default. I just reverted to default settings when trying to convert a mobi to epub, and the options to remove/insert paragraphs, linearize tables and several other obvious unwanted modifications are all disabled.
If true, that's excellent news! I've carried around my custom Calibre settings for several years now, so I don't really know what is the default anymore. Back when I started using Calibre, the default settings were not ideal, and most Calibre converted files I've seen in the wild have used the old defaults.
KF8 is a proprietary wrapper around a regular EPUB file.