Last year we were discussing in Revenge of the Sith if the Emperor was feigning death when Mace was about to kill him. We went back and forth on it bla bla bla

Well it looks like we have some clarification from the "Star Wars Insider", Special Edition 2010. On page 110 they say that the Emperor was in fact feigning death.
Here are the excerpts:
"The scene was rethought after principal photography, and it was decided that Anakin should not come in until later, when it appears that Windu has won.
As Palpatine feigns weakness and pleads for his life, Anakin is forced to choose his loyalty.
"When Anakin steps to his defense, it becomes clear that the Sith Lord is not as weak as he appears to be. Palpatine easily dispatches Windu...."