Interesting thoughts. Here is one interpretation to chew on: When Palpatine “died”, the persona of Sheev Palpatine sort of died on the Death Star, but the spirit survived. It is almost like the shell of Palpatine was shed, and what we had left was this Sith incarnate. Technically it is the same entity we knew from the PT and OT, but it no longer tries to hide its true persona. It definitely would make his return creepier than this one dude just still being alive somehow.
I’m kind of curious if this Sith incarnate is the spirit of Darth Bane passed down from vessel to vessel, or with each new host the Sith spirit becomes a collective consciousness.
My take was the latter; I understood the hooded figures in citadel to be spectating Sith spirits who dwelt within Palp, though apparently I am wrong. According to wookiepiedia those were the Sith cultists? I thought the contrast was the show of arrogant flaunting of power of the sith vs the minimal but more powerful incarnation of the Jedi to Rey.