SM
Bigfooty Legend
Meaning he's transitioned to force ghost, force is inherently neutral, there's no position that "light" ghost is unable to transition to "dark" ghost and flip flop, thus Vader is not truly dead as it is Anakin as ghost.
You are suggesting that there is zero chance of a flip, considering we've seen taint of armour is still "dark" so there must still be residual "dark" energy within the universe tied to the person.
Dark Side users can't come back as Force ghosts though.