The Combat Expertise feat's notes make it seem like it is an upgrade/replacement to defensive fighting. Is that the case? It does basically the same thing, but at a lower penalty to the character.
If it doesn't replace it, then the two could be used together since dodge bonuses stack.
My main reason for answering is that I originally read the description to read that it does replace defensive fighting, so I've been allowing a character with the Two Weapon Defense feat to gain the higher bonus from that feat (as if he were Fighting Defensively) whenever he uses Combat Expertise.
I'm uncertain about that now ... although I'll likely stick to my original ruling. His AC is typically among the best in the group, but even with this additional bonus he's only a couple of points ahead of the others.
If it doesn't replace it, then the two could be used together since dodge bonuses stack.
My main reason for answering is that I originally read the description to read that it does replace defensive fighting, so I've been allowing a character with the Two Weapon Defense feat to gain the higher bonus from that feat (as if he were Fighting Defensively) whenever he uses Combat Expertise.
I'm uncertain about that now ... although I'll likely stick to my original ruling. His AC is typically among the best in the group, but even with this additional bonus he's only a couple of points ahead of the others.