i feel the reason that qui gon didnt disappear is simply because he didnt know how to..and in episodes 2 and 3..when the jedi start to be killed off..yoda...obiwan..and a few of the remainin jedi learn to come back cuz they know they will need to...and thats why obi wan knows how and jin doesnt...
i think
well I think it's all because of how good a jedi you are.
vader being the chosen one, is of course able to fade
OB1 is one of the best jedi who are left in the OT so he fades
Yoda, doesn't need more explaining if it's this theory
how much I love QGJ (ask yerss I think the guy owns) he wasn't powerful enough a jedi to fade
It's nothing to do with EU, Fire.
Everything we have in the films makes it clear that the disappearing trick is NOT something that Jedi normally do. The crux line is
"Strike me down and I will become more powerful than you can possibly imagine," followed by Vader's confusion at the disappeared body.
This is not something that has happened before; it is unique to the Jedi in those films.