My point was that to the plot and the twist trick it wasn't important really if it's a clone or a real brother.
I disagree with the notion that it doesn't matter whether Borden is a set of twins or a set of clones. It degrades the themes and characters in the film if Borden is not a set of twins.
Borden understands the struggle of Chung Ling Soo because he himself also has to appear publicly as something he is not. Two people with different goals, values, and desires presented as one person in order to maintain a magic trick. And this is why it's so tragic. Only one of them is obsessed with maintaining the illusion of one person to perform the trick, and it results in both of them suffering greatly.
Borden as clones is also inconsistent with other things presented in the film. Bale's performance has some great subtle moments where you can see that he's actually acting as two different people, and Borden doesn't witness Tesla's show until after
he has already done his transported man trick at least once for an audience.
Well yeah, I never thought that him having a clone makes complete sense in the first place, but assumed that it's possible just for the sake of some people in this thread and in other threads who still think Borden and Fallon are clones (and for the sake that I might be missing something as well). But no, as you pointed out, he can't really be a clone, which I think I said in my first post here, but when I said that 'twins/clones -> doesn't matter' I guess I contradicted myself.
Therefore yes, it does matter because the second (the clone variant) shouldn't make sense.
However, if Borden and Fallon weren't noticed to act differently, then I believe it wouldn't have had any difference to the twist trick.
What makes me wonder is what differences did you actually notice apart from the women the brothers loved.
I think that's debatable.
1st: We saw Borden act controversially towards his wife. Namely guessing that it's because sometimes it's Fallon. If i remember right Fallon loved Sarah and his daughter and Borden loved Olivia. What one should notice here is that... the fact that Fallon treats his wife one way and Borden treated Fallon's wife in another way (he was rude to her, fake and impulsive towards her) this doesn't mean Borden and Fallon have different characters. Borden was just stuck on his duty with Sarah, who he didn't sincerely love, so it's safe to say that we can understand why he didn't have the unlimited patience either. In the meantime we see Borden loving and treating Olivia with kindness and sympathy (because he felt sorry for her cuz Angier only used her), while Fallon only wanted to use her in the first place, before he knew his brother is in love with her. We can see they're both equally cruel and diabolical towards each other's women, but also equally loving to their own.
Conclusion: Borden and Fallon's attitude towards their own beloveds was quite similar. Fallon and Borden's attitude towards EACH OTHER's beloveds was quite similar too. And for a reason. In other words they behaved the same way around the person they loved and they behaved the same way around the person that they didn't love. Having cleared that, then these 'differences' aren't really any differences that should give us enough reason to think that they had different characters.
Only one of them is obsessed with maintaining the illusion of one person to perform the trick, and it results in both of them suffering greatly.
I think I disagree here. At least I don't believe there's proof. We can assume that it was Borden who told Angier the thing about sacrifice in relation to Chung Ling Soo's act. But then at the end we see Fallon talking about the same to Angier, who's dying in the same time. In other words we can see him agree with Borden. In addition to that I don't see how it's possible for Fallon to do all those things JUST to help Borden in his obsession without Fallon being obsessed with the same too. I mean ok, they're brothers, they're supposed to do favors for each other and help out, but all this? Really? Fallon's either equally obsessed or totally insane and just wondering how to ruin himself or what to do, like there's nothing really better to do. Or some other reasons? Nah. Somehow i seem to be in favor of the possibility that they both were equally obsessed. But do notice, I'm still not saying they're clones.
In point 1 and point two I've pointed out the things they're kinda equal in but one little line just bugs me and keeps rotating in my mind. I mean so far in pt1 and pt2 they're acting like clones but... When Angier performs The Real Transported man for the first time we see the brothers arguing. Actually one of them is arguing. We can't really tell if it's Borden or Fallon cuz we don't really know whose turn it is to be each of them. But we see one of em sitting on the desk staring at sketches and drawings, thinking or at least trying to think. And we see the other one yelling at him saying 'WHY CAN'T YOU OUTTHINK HIM???'. This might possibly mean that one of them is different, a thinker, a schemer, smarter, while the other one is the leader. If this is so then they are brothers and not clones. But on the otherside it might not mean that. He might just be saying that. However, even if they're clones, Borden is bound to be the leader, namely because he's the original and the other one's a copy. But that won't make them different in spirit, mind and soul. (tho that's debatable too, the only different thing inside their memory will be on which side of the machine each stood when the cloning happened [if they're clones that is], but before that they'll both remember that they both stepped into the machine, so this leader thing is also very unstable as an idea)
This is the only scene we see with both of em act differently in the same scene, while talking to each other. There's this other scene where they cut their fingers, the other one where they swap disguise and the one in prison, before execution, where they both cry and where Borden says to Fallon that he's sorry and that Fallon was right that they should both leave him alone to do his trick. This proves that Fallon was the one that said 'WHY CAN'T YOU OUTTHINK HIM???' then followed by the decision that 'We're done' and that they should really leave him alone. That means Fallon was the one that was yelling and was being agressive in that scene and Borden was the possible 'thinker', which pretty much makes Fallon the leader if that above-mentioned idea is right and if they're really much different while alone without anybody around. Anyway, that also means that if you're right then Borden's more obsessed because he couldn't help it but go and see Angier's new trick. Which also assumes that Fallon is more agressive in that one scene and then a murderer because he shoots Borden (even though he decided to 'go too far' just because he wanted revenge, which makes him different from Angier because the thing with Angier's wife was a mistake, but Angier framing Borden up was nothing but deliberate, which doesn't make Fallon look all that bad, just more brutal than Borden. Just a bit. I mean really, one can also debate on what the chances were of Fallon having the idea to break his promise and go to see the Real Transported Man. I'm sure that there wasn't much keeping him from doing it, he just decided not to, it's not that he wasn't tempted. And he had many good reasons after all Angier did, so.)
As you can see I'm trying to argue with myself in the search of the truth behind all this, but it's too complicated and depending on many uncertain factors. Most of the confusion comes out of the fact that:
We have Borden as himself. (1) (looks like Christian Bale)
We have Fallon as himself. (2) (looks like Christian Bale)
We also have Borden as Fallon with beard. (3) (This here is Christian Bale with a beard and a hat and a rapist coat)
We also have Fallon as Borden. (4) (looks like Christian Bale)
We also have Fallon as Fallon with beard. (5) (This here is Christian Bale with a beard and a hat and a rapist coat)
1, 2 and 4 look the same.
3 and 5 look the same.
1, 2 and 4 don't look like 3 and 5.
And that makes it a 3 to 2 in favor of Borden. We as the viewers are doomed to connect Fallon with the bearded molester-looking guy, while only the name connects him with it. We can't be sure who exactly spent most of the time doing Borden or Fallon. I mean, (if they're brothers) before they had the idea of using disguises they both looked the same all the time (maybe just avoiding showing themselves simultaneously in front of people). Just because the bearded guy was also named Fallon we mustn't really connect him to the real Fallon, at least not as much as we do.
Anyway this whole wall of text wasn't really to counter your last post but just debate and trying to work out some shit. Now I'm even MORE puzzled and can't really decide on whether they're really acting differently or not. It's not really that underlined and emphasized in the movie.