I love this sort of exchange. Thanks to all the contributors for helping me learn a little more Spanish every day, and for sharing my enthusiasm for it all. I really like Benilde's explanation of "mis más..."
I would have guessed that "mis más espontáneous comentarios" would be "my most spontaneous comments" and "mis mejores espontaneous comentarios" would be "my best spontaneous comments." One is a statement about the degree of spontaneity and the other is a comment on the quality of the spontaneous comments.
So, the original quote would be translated:
Mis mejores espontáneos comentarios habían sido elaborados días antes.