I think the whole Mace/Sidious scene seemed very rushed, and wasn't helped by Anakin's ridiculously speedy turn to the Dark Side. Whether or not Mace was supposed to live or die, I can't imagine why it would be left ambiguous, unless it was just sloppy storytelling, which wouldn't be a shock in the prequels. Plus, the ambiguousness is even more perplexing when considering the aforementioned absence of the character (or at least the character's name) in other SW stories.

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Whether sidious was simply faking his defeat when Anakin walked into the room is still unknown, however

I thought it was pretty obvious that he was "faking" it for Anakin's sake, so Anakin would intervene and take care of Windu. Like, "Oh no, help me, this bad man is hurting me!" But again, the scene was kinda sloppy, and could've been done more smoothly/naturally.

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Sadly, Lucas chose to follow the movie cliche of having the black man die

Lando lived-- score another point for the OT.