Not sure if Hal you care about this, but I certainly would like to remove all the “random” voices during that “Jedi chatter” scene and not specifically for canon reasons.
Fan edits do not need to follow cannon since … well, any change to a movie breaks the cannon anyway, but for the audience watching the movies and hearing a bunch of “random” voices that were not heard in the previous movies is jarring … to me at least thinking of the “average” movie watcher going from Episode 1 to 9.
(I agree with the others here about not having the other Jedi voices in that scene since … pre disneyified “canon” that only a couple of Jedi were able to do so via special training that was explicitly mentioned in Revenge of the Sith … but Disney already broke that logic/canon with Palps. Sith cannot live on prior to Disney… which is why Plagius was trying to find a way to reverse dying and live on but was cut short by Palps. Plus, George Lucus explicitly said Sith were not able to obtain it, just the Jedi via their absolute selflessness which made it ironic the Sith who wanted to live forever could never obtain it via the dark side … only the light side for the side who do not care about themselves. But we know what happened, RJ decided “Hey, Sith live on too! They just keep going to the next body” which then kills the whole narrative of Revenge of the Sith. That concludes my TED talk.)
Wait, why are you blaming Rian Johnson for that? Rian Johnson didn’t do that, lol. Rian Johnson was not involved in bringing back Palpatine, lol.
On the subject: Sith can’t persist as bodyless spirits, but they can persist if bound to objects or host bodies (and host bodies is something literally only Palpatine has ever achieved, and only through what he’d learned from Plaguis before turning on him), though it’s an extremely unpleasant ‘existence’.
Anyway, there’s a difference between reaching into the netherworld of the force and making brief contact with old friends, long gone, than a ghost manifesting in the material world, a la what Obi-Wan, Yoda, and eventually Luke and Leia learned.