My bet goes to the select few...the people think he's the hero, so why say you are a Sith Lord who's been after the extermination of the Jedi for a couple of centuries!!!!
But I believe there are more than at least 5 topics on the Palpatine/Sidious-plan/appearance/do they know/etc-issue now....and more if you count the past ones in.
(perhaps the moderator would be kind enough to merge all these threads).
Palps is the intergalactic equivalent of Hitler, who also started out as a Chancellor who won the people over. Fearred by his people, who are kept in line with an iron fist and blinded by the propaganda he spins. He has supporters in other planets, has alliances, and that's how he can set up the Imperial Academies across the galaxy. Even the Stormtroopers are inspired by Adolfs shenanigans.
Palps keeps everyone in line with fear. I'm sure he has a few true supporters, but I'd say most people are scared to death of him and don't want to be punished for showing insurrection.
I mean, given the right spin on things, everyone could know that Palpatine is a Sith Lord and not actually mind, much like how many people knew that Hitler was a murderring, homocidal racist and did nothing about it because they were brainwashed into thinking he was fighting the good fight. Or they all know he's a Sith Lord and are just quaking in their pants.
It's obvious either way that Palpatine is fearred, rather than loved, by the time ROTJ ends.
It's kinda funny how The Clone Wars mimmick WWI, and the Galactic Civil War mimmicks WWII.