I don't think he was using the force to make people not see his true face. Perhaps he was using the force to maintain that appearance against his age and he wasn't able to hold it up under concerted attack, though. If he actually looked like that before the attack, I would think we'd have seen him using that appearance when speaking to the people who knew him as Sidious, but what you can see under his robe's hood he still looks pretty normal throughout the prequel era, iirc.
Yeah but as we all know the hood was so he wouldn't be seen as Senator Palpatine while concocting his inside upheaval with his cronies. I just figured he flipped it on when he had to make his video calls.
And I agree that he was just a drained old fart more or less and not scarred but used that appearance to explain how his appearance changed so radically and so quickly.
I honestly don't dig much into the prequels like I did the original trilogy. As someone who saw ANH at the drive in in the 70's, my heart just isn't in them...whereas I scanned over every minutiae of the OT as a kid onward...so if this has been explained already, I am obviously ignorant of that. These are just how I have interpreted the prequels in the handful of times I could stomach them.
Luke suffers Force lightning for quite a long moment in ROTJ but doesn't get any facial scars.
And see this just reinforces my view on all this, however, you also have to factor in the whole "Duh, it's Lucas" slant and then it leaves you even more confused and back to square one. :|