Nifft said:
See, I disagree that sight is the only useful sense. I think you can feint with sound (yelling "Hiya!" when not striking) and touch (the tip of your weapon on his shoulder and such) as much as you can with a visual mis-cue.
-- N
Yes, but if he's not able to clearly perceive what you're doing, I.E., for most creatures, by seeing you, feinting isn't meaningful. To touch him with the tip of your weapon would require a touch attack....but merely touching him with your weapon doesn't do anything to him except alert him to your presence. Shouting at him, similarly, wouldn't accomplish anything other than alerting him to your presence. Sure, you might startle him in the process, but that's not going to create an opening that didn't exist before: While he's aware of your presence, he's not aware of what you're doing. Since he can't perceive a feint well enough to believe it to be an attack of any kind, he can't be feinted. It's no different from being unable to sneak attack an invisible, non-moving person: You know he's there, he's not attempting to avoid you, but you simply can't perceive enough fine detail to effectively strike at his sensitive spots. You can't mis-cue him when he can't perceive you well enough to take cues from you in the first place. One thing that you COULD accomplish by shouting at him would be to make him aware of your presence....as such, this might allow you to achieve flanking, which could grant you sneak attacks. This, however, goes back to "can invisible people flank while undetected"?
Now if he had blindsight or an any other ability that would allow fine perception of an invisible person, then he could be feinted. This may seem like having blindsight is actually a disadvantage, but once again, it's in ability: It's not inherently advantageous or disadvantageous, it merely exists. Like conditions, they can be used in an advantageous manner, or an enemy can turn them against you. It's just like how in Judo, being stronger than your opponent isn't necessarily helpful, if he can just turn your own strength against you.