Fixed. Also changed the description of the lizard limbs trait, and tweaked it a little bit. Everybody gets +3 healing rate (will work only on new chars unfortunately), and the lizard limb trait simply caps healing rate to 5. The amount healed is also rounded up, rather than down, when the HP calculation occurs.
So in all, even with lizard limbs, you will wake up (eventually) after being knocked to negative HP.