Originally Posted by DuckieTigger
Some KF8 have the font hard-coded into the book. Very annoying. One way to get rid of that is to run it through Calibre with a mobi to mobi conversion and select ignore font settings (font filter or somesuch). Converting to old mobi format should also work. Of course, to do any of that you had to free the book of its DRM.
Don't do that. It's not a Mobi > Mobi conversion. It's a KF8 > Mobi conversion and that's a very bad idea. If you can strip the DRM, you can use Tweak Book in Calibre to get access to the CSS and OPF to remove the fonts as well as being able to delete the fonts.