Wings of Redemption
As a special case, 0 Nonlethal Damage is a special non-comparable value. That is to say, 0 Nonlethal Damage is neither greater than, less than, greater than or equal to, less than or equal to, equal to, or not equal to any value of damage. Thus, creature that is reduced to negative HP, becomes stable and eventually conscious may act while disabled if they have 0 Nonlethal Damage (that is, the 0 Nonlethal damage is not considered to be greater than their current HP total of, say, -5). If they had 1 point on Nonlethal damage, they could not regain consciousness until that went away, however.
Nonlethal damage is considered a form of hit point damage.