I question if they were ever really incorruptible. I suspect there was a lot of looking through rose colored glasses when it came to the Jedi order's past. At best, they probably were just better at catching the bad eggs before they went too far. Lesser numbers and too many distractions probably led to the order's downfall.

I was speaking of the matter of perception. To most of the universe, Jedi prior to the clone wars were wise, powerful, and nearly un-killable. They were viewed with a sense of awe and wonder, or terrible dread if you were doing something illegal! The Clone Wars changed a lot of perceptions though. Jedi died in serious numbers vs battle droids. A former Jedi Master, Dooku, was leading the Separtists. The Jedi's shiny badge of perception was seriously tarnished during the war.

So they had better PR?

Or more likely, Palpatine never did anything to arouse suspicion that he was anything more than an elderly politician from backwater system, one that managed to capitalize on his world's invasion to ascend to the highest office.

If the Jedi have no reason to suspect he's any kind of Force user, especially if his medical records show that his midi-chlorian count isn't worth a second look, they're not going to randomly start trying to see if he's a Force user.

Per RAW in this system, if you're not actively using the Force, then there's no way to tell if somebody's a Force user or not. Granted, many GMs have allowed the usage of the Sense power to pick up on that sort of thing, but that's more of a house rule, and the Jedi Council aren't a bunch of paranoid PCs.

Or more likely, Palpatine never did anything to arouse suspicion that he was anything more than an elderly politician from backwater system, one that managed to capitalize on his world's invasion to ascend to the highest office.

If the Jedi have no reason to suspect he's any kind of Force user, especially if his medical records show that his midi-chlorian count isn't worth a second look, they're not going to randomly start trying to see if he's a Force user.

Per RAW in this system, if you're not actively using the Force, then there's no way to tell if somebody's a Force user or not. Granted, many GMs have allowed the usage of the Sense power to pick up on that sort of thing, but that's more of a house rule, and the Jedi Council aren't a bunch of paranoid PCs.

I was thinking beyond the system... there are disturbances in the Force, Force users seem to sense each other's presence all the time, etc... and yet one of the most powerful dark side users in the history of the setting is standing within meters of the multiple Jedi masters at several points and they feel nothing...

E: typo

Or more likely, Palpatine never did anything to arouse suspicion that he was anything more than an elderly politician from backwater system, one that managed to capitalize on his world's invasion to ascend to the highest office.

If the Jedi have no reason to suspect he's any kind of Force user, especially if his medical records show that his midi-chlorian count isn't worth a second look, they're not going to randomly start trying to see if he's a Force user.

Per RAW in this system, if you're not actively using the Force, then there's no way to tell if somebody's a Force user or not. Granted, many GMs have allowed the usage of the Sense power to pick up on that sort of thing, but that's more of a house rule, and the Jedi Council aren't a bunch of paranoid PCs.

I was thinking beyond the system... there are disturbances in the Force, Force users seem to sense each other's presence all the time, etc... and yet one of the most powerful dark side users in the history of the setting is standing within meters of the multiple Jedi masters at several points and the feel nothing...

Sith dark side techniques and/or sith sorcery to hide the fact that you are a force user, iirc there are even sith techniques to masquerade as a light side user.

Well, at least in the new canon we really haven't seen enough of Luke post-RotJ to really see where he falls. He was generally a good boy through ANH and ESB, so he probably didn't earn much (if any) Conflict, so a case could be made that he'd made it past 70 at the very least. RotJ he got a bit darker, or at least was more willing to use those dark side pips, but at the end he probably still ended in the low end of LS Paragon at the least.

So like, when Luke cut off Darth Vader's hand on Death Star II and paused to look at his own hand, he wasn't thinking of the similarities between himself and Vader—he was using his fingers to count how much Conflict he'd accrued that session...

(Caption: aboard the second Death Star, Luke stares at his gloved, mechanical hand)

"Crap, there's no way I can get away with killing him now! I'd lose my paragon status."

Well, at least in the new canon we really haven't seen enough of Luke post-RotJ to really see where he falls. He was generally a good boy through ANH and ESB, so he probably didn't earn much (if any) Conflict, so a case could be made that he'd made it past 70 at the very least. RotJ he got a bit darker, or at least was more willing to use those dark side pips, but at the end he probably still ended in the low end of LS Paragon at the least.

So like, when Luke cut off Darth Vader's hand on Death Star II and paused to look at his own hand, he wasn't thinking of the similarities between himself and Vader—he was using his fingers to count how much Conflict he'd accrued that session...

(Caption: aboard the second Death Star, Luke stares at his gloved, mechanical hand)

"Crap, there's no way I can get away with killing him now! I'd lose my paragon status."

Nah, that was him counting his Dark Side Point total under WEG's d6 system

Is it ever explicitly explained how someone who amounted to a "dark side nexus" managed to so thoroughly hide his nature for years while right under the nose of the most powerful Jedi in the galaxy?

Palpatine used the Sith shrine under the Jedi Temple on Coruscant with his own Sith sorcery to weaken the Jedi's ability to commune with the Force.

http://starwars.wikia.com/wiki/Sith_shrine