Originally Posted by Hekse-Mie
With the 2.4.0 update, I had to remove all references to other fonts in the stylesheet. This way Century Gothic (and other fonts) work fine now
If the epub specifies a font, as you said, your Kobo will not override that. Much as a line height specified for a paragraph will not be overridden by the Kobo's line spacing control and the margins control will only increase stylesheet defined widths. My guess is that Kobo is trying to leave the format close to the way the ebook publisher designed it (or is that Adobe since epubs use Adobe Reader Mobile to render).