Yeah, I don't know enough about bows to comment on that, but it's pretty obvious nitpicking. As for the rest, yeah, I agree. People can rage when the game comes out and turns out to be shit, but this one shot barely shows anything. As I've said, it's hopefully just overreaction from the commenters.
And it just might seem brighter because of the photo quality.
Quick edit: I can't seem to remember any time in the Thief games when the light gem was "not in use", since it's such a core part of the gameplay. Even when you're aiming, it's good to know how hidden you are. But yeah, I doubt they're getting rid of it.