Originally Posted by _savage
Yes, it seems to be that way. Is there a list of compatible features and common denominators across these formats? Something like a "Don't do this in EPUB if you want to generate a MOBI?"
The MOBI source file format is documented and HarryT has written a great tutorial on how to prepare files for use by Mobipocket Creator. This tool is in the wiki with links to both Harry's tutorial and one that is located on the Mobipocket web site. This will tell you exactly what you need to do to make a .mobi by hand. Note Mobi does not support any CSS at all so the KindleGen program converts some CSS into a form needed my Mobi. The Something like Don't do list changes every time Amazon releases a new KindleGen.