Mr lizard I’m with you most of the way but in terms of the movies I think we can let Anadins ghost of the hook. The only person we know gets to see them is Luke. There is some talk of Qui-gon contacting Yoda from the Netherlands or something but we don’t really know the rules. Palpatine could be talking to him via his grandaddy’s hat. Maybe only people who met them in life get to see them. Qui-gon doesn’t turn up to give Luke advice. So as far as I’m concerned the ghost thing isn’t an issue.