Originally Posted by DiapDealer
The problem is that a mobi book is a binary database file that must be built from its html source. Epub is source that's zipped up. A binary mobi file editor would be a fairly large undertaking (especially since there are still a few mysteries being slowly revealed about the proprietary format). It's much easier to convert... fix... and reconvert than it would be to code a wysiwyg binary mobi editor. And frankly... the end result wouldn't be any (OK... much) different anyway.
It's just easier to convert to another format and edit. I don't mind the Calibre code. It how it looks and reads on the reader that counts.
I don't care for Sigil it's a little slow but I have used it once or twice. I like using Word 2003 cause I edit pretty quickly what I need with my Macros I made.