Dramatic difference between carnivore and normal
I like playing kobolds, and I got a draconian with the carnivore mutation recently, and I've just got to say, it's the most powerful mutation ever. In anywhere corpses are dropped, you can stay at satiated all the time, and still spam honeycomb-hunger spells, or go berserk in every combat - even with the single level of mutation. You get the benefit of a full nutrient reservoir at very little cost (bread rations give slightly less nutrition - big deal!)
I suggest that the different levels of herbivore/carnivore mutations should have a more effectively incremental effect. (I may have suggested this a year ago, but I can't find it in the tracker, so please bear with me. Maybe it was on IRC.) The most important change would be this:
3 herbivore - no chunks ever, as spriggan
"You can't eat meat."
2 herbivore - chunks only at near starving or less :
"Yuck! You're not desperate enough to eat that yet!"
1 herbivore - chunks only at very hungry or less
"You're hungry, but not hungry enough to eat that"
normal - chunks at hungry or less, as today
"You're not quite hungry enough to eat that!"
1 carnivore - chunks until full
"Gulp. Your stomach isn't quite ready for that yet!"
2 carnivore - chunks until very full
"You're a little too stuffed for that!"
3 carnivore - chunks until satiated, as today's kobold.
For quality persistent food, like rations, I would like things to behave as today for people with no mutation or three levels of anything, but for one or two mutation levels, you could possibly limit eating the wrong type at full or very full.
I also suggest getting kobolds down to 2 levels of carnivore, trolls at 3 (can they eat veggies at all today? If so, maybe adjust down their hunger slightly to balance the disadvantage), and put Ogres back at 1. Spriggans still at 3 herbivore, natch. Maybe switch out the centaur's high metabolism with slow metabolism and herbivore 1 (I find the idea of ruminanting centaurs amusing)