So this came up indirectly pre-game last night, so I need to clarify a few things.
The rules on p 17 state that stress prevents actions, even free actions.
So firstly, Turr Phennir's ability would not be usable if he was stressed (as it is a free action).
And secondly, even Squad Leader would not be able to help a Stressed out ally nearby.
Are these instances to follow the normal rules (above), or exceptions somehow?
And so a "free action" is only "free" in the sense that it is an additional action on top of your normal on in the activation phase.