I read the supposed plot for sw ep 9 and it said "The Jedi meet at Yavin 4 to celebrate the defeat of the dark side. In the distance, Luke can see countless thousands of Jedi from every era appear as Jedi spirits". I think it has something to do with the dark side not alowing them to transform into the force, I don't know about qui gon but darth vader could have if the statement is true because he was not held back by the dark side. (I hope what I said wasn't confusing)
Never UNDER ESTIMATE a Jawa.