Bingowings said:
I know that Ben's ghost scene isn't much of a retort from Luke but it's all that we can get and just having Luke stumble on the truth at some point isn't something that can be done with the existing material.
If Lucas had done it properly we we would have shots of Luke noticing Skywalker style behaviour and then we he tells Leia (or even when he second guesses Ben's ghost in the existing versions) it could have been a semi-plausible revelation but then if Lucas had been in a mind to do it properly Leia would never have been the Other in the first place.
Leia does show Skywalker style behaviour but he's hardly ever around when she does it, (choking Lando via Chewie, choking Jabba, rushing in to save Han, sensing Lando isn't quite right etc). If anything Luke is more likely to conclude Han is his sister going on the evidence he's around to see.
If Luke had been around to notice these things at least Ben could then argue he was trying to protect her from herself and that Luke showed less potential for going the same way Anakin did.
So if we have to have the Ben scene (and I fear we do) putting him on Tatooine where he has a strong connection to Luke makes more sense, to me at least, for all the reasons I've listed.
Vader figured out Luke was his son without being around him (of course, if we go by Skywalker being the actual last name, then it wouldn't be too hard to figure out that connection. Then again, why didn't Vader know that Luke was his son in ANH, being that someone would have told him that the droids were owned by an Owen Skywalker, father of Luke Skywalker... ah, the paradox of Lucas' mind).
Even so, it is a correlation to how Vader confronts and enlightens Luke at Bespin with Luke's revelation to Leia on Endor - the scenes mirror each other. My point is that Luke figures it out through his connection to the Force, much as Vader no doubt figured out Luke's identity through the Force as well. Being a Jedi master is about being a master of yourself and your own path, not being told every little thing like a child at school. In fact, it surprises me that Lucas did not keep the reveal to Luke's conversation as it happens near the end (like the one in EMPIRE) and it would have had more impact than a casual conversation in the beginning of the film.
It also shows Lucas' inability to allow the film's story to flow into revelations, and shows us his lack of faith in the audience by having Oli Wan Ricobi literally spell things out in the most banal way possible.
But, to quote a more well known philosophical a-hole, "that's just me, I could be wrong."
