Does anyone know how to turn this off?
Apparently I'm not the only one with this problem, nor is it limited to the PC version. The highest rated Amazon.co.uk review for the Xbox 360 version of Dishonored has this to say:
I found the only real complaint I have with this game; the context-glow (or focus-glow, if you will) of items still exists whether you turn it off or not. That's a bug, which I hope will be fixed because it does detract from the immersion. Not massively so, however. Just enough to recall that you're playing a game, and are not totally part of the world.