It all depends on the size of the nail, and the size and speed of the saw. Those chainsaws professional loggers use go very fast, and if they hit a nail in such a way that it dead stops then the chain usually breaks and becomes a projectile. Spiking trees was a major hobby of Earth First for a while.
That’s why I wear the Kevlar pants.
A broken flailing chain hurts, but won’t slice my leg.
Been hit in the helmet and face shield. THAT’s ‘exciting’