Well, as far as a classical film reason for the mirror image (and I keep posting this in other threads, so you guys are probably sick of me), the simplest example is if you have two characters talking to each other in profiles. If they're both facing the left side of the screen, yet talking to each other, the audience is going to be confused. It looks like they're facing the same direction. So you have to flip one of them, so they look like they're facing each other in the cuts. it's called "crossing the axis", and puts an imaginary line from person A's face, to person B's face, and the camera cannot cross it. When you add in reaction shots from peripheral characters, it gets more complicated. The best example in Star Wars for the axis crossing is at the end of ESB, I think it's Piett who has his rank thingie on the wrong side of his chest. The reason is that they'd already established which side of the bridge he and Vader were on, and Vader was facing one way, and they'd filmed Piett was the correct way, but on the wrong side of the bridge, so they had to reverse it. Make sense?
And yeah, that's something I noticed when I saw ESB in the theater for the special editions, about Fett looking down that hall. I just assume he was looking at Luke though. And that's why the ANHSE is so jarring to me, he looks right at the camera, no denying, and breaks the fourth wall. Very disturbing to me, as a film dork. The others you can say he was looking at Luke, R2, or just waiting for those Bespin guys to stow Han. But the ANH one, he is so damn blatant about it...it ruined the whole scene for me. (I mean, even ignoring the not so great cgi Jabba.)
