I mean, the Force Spirit ability isn't about how powerful you are with the light side -- it's about completely and utterly knowing yourself on a fundamental level, and fully embracing the Living Force... It's also an ability that even the Jedi believed was impossible, until Qui-Gon's spirit came to Yoda and told him about the Priestesses.
Perhaps it also has to do with The Ones solely embodying the Cosmic Force... Granted, the Living Force feeds/powers the greater Cosmic Force, but they are still treated as two different aspects.
The only issue with that is The Father, as he disappeared/sublimated into the Force after his death... So he clearly knew the ability, but evidently just never saw fit to teach The Daughter how to do so, despite the untold thousands of years they spent in isolation together.
That being said, I suppose you could argue that The Daughter may have achieved a resurrection of sorts, in the form of Morai. /shrug
Originally posted by Galan007so ive been looking for an answer but can't find one.
No clue when Vader would have learned the ability. Logically, it would've had to be sometime between him throwing Palpatine down the reactor shaft, and him 'dying' in Luke's arms... How in the f*ck he was able to master such an advanced Jedi ability in a matter of minutes is another story...
I take it that is was never explained how or when Anakin learned to become a ghost?
How or when? No.
All we know is that Yoda taught him the ability:
https://i.imgur.com/WnJHmh8.jpg