An animation industry animator (click on the picture) described Line of Action principle to me as:
"The LOA thing is always a killer...
1) HOW THE CHARACTER IS FEELING.
2) WHAT THE CHARACTER IS DOING WITH ITS ENERGY
EVERY CHARACTER POSE MUST HAVE A LINE OF ACTION THAT SHOWS THESE TWO THINGS!"
Yes, he did use his "All Caps" voice because it is very important. The incident (pictured) was captured on a security camera (click here to see the footage).
To paraphrase Leonardo da vinci, "The ... attitudes of a figure should display the state-of-mind of him who makes them and in such a way that they cannot mean anything else."
Image used for educational purposes is from Toy Story © 1995, Walt Disney Pictures