Can one "attack" defensively when the action being taken is not, strictly speaking, an attack? For example, a disarm or feint?
Only if the action can be used in place of an attack action. Disarm functions this way, but Feinting does not.
If I was your GM in a home game I would probably allow this with the attack penalty applying to your feint check. Check with your GM.
But in a PFS game this will not work.
Peet
Isn't that effectively what Combat Expertise does?
You take a penalty to hit and get an AC bonus..it even scales!
@Blindmage, yes and no.
They are two separate mechanics that work alike.
Fighting defensively causes a -4 penalty to hit but grants a +2 bonus to AC. Anyone can do that, even without Combat Expertise.
While Combat Expertise grants a scaling -1 to hit and +1 to AC (1-per-1 trade).