I'd have to think about that one...
I've always thought of macs as pretty straight forward. And it in some cases with a mac, is less about the body language by itself, and more about just familiarity with the bird, and the body language in context of the situation.
A spikey head, and eyes pinning may mean I'm goofy, and happy to see you... It may also mean that I'm territorial and becoming pissed...
Going big bird usually means I'm fixin' to attack. It could also mean, "I'm wound up, let's play."
Bluffing can be play and/or an invitation to play. Or it can mean back off, you make me nervous. Or it can mean I just wanted to see how you would react, and whether you were afraid of me. Or it can mean this is my territory I'm going to rip your lips off...
Without a context... what good is this information?! "Could mean a lot of exact opposite things" Is not a very useful post. You're bleeding?! In your case, I think it meant that the bird was about to bite you...
I can usually tell just by looking at them, which birds are going to attack me, and which aren't. But it has more to do with overall mannerisms... the way they hold themselves when I approach. Certain looks...
It's less a universal truth.
There is no line of death dance per se... with a macaw.
BUT when you have a territorial macaw, IT IS JUST A GIVEN that a stranger entering the territory uninvited will get lunged at. TAKE IT AS FACT, AND TAKE STEPS TO PROTECT YOURSELF. YOU JUST KNOW...