Hmm...okay, I think that left me a bit more confused.

Now, I know Darkness and Cover are different. But, wait...why would a maneuver called ''Blind Fighting'' not help you fight in the dark at all? I mean, granted, if you are attacking a target you can't see you're effectively blind...but...I assume full cover is ''Hiding Behind a Wall.'' Or some such thing. How does Blind Fighting make it easier for you to...bend around a wall and hit them? I would just move behind the wall so I get NO penalty. If they are behind a wall all the way then chances are I'm not right next to them, thus negating my ability to hit them anyway. So it's a useless maneuver, by those standards. Unless it magically allows you to bypass a wall when you have it(since it goes from -6 to -3.)
As for the power, it just says ''negates full darkness'', yes...but I'm just curious WHY it wouldn't just make it easier to fight in the dark(sort of like vision mods do-how thermo negates full darkness to a minus whatever it was.) If you can even see the outline of a target, does it just...stop working?
If these are the cases, I think I might have a new houserule coming up. Especially for the maneuver, unless there is something more to it than I'm not getting. ''Can't See the Target'' either means they are in full darkness(which it apparently doesn't count for), behind a wall or car or something(which means I can't hit them anyway), or are behind me(in which I take a free action to turn around.)
Oh yeah, it's also weird that someone with -3 would take worse penalties than someone with -6. In that way, the person with -3 vision should end up getting 10 BP, and the -6 only 5, since it seems easier to deal with.

(though that's one of those flaws that's rarely ''taken for points'', I admit-ie, not an Allergy or something.)
EDIT: Okay, re-read Blind-Fighting(Maneuver.) Apparently, it's only good for fighting Invisible targets, or of you're a gunner of sorts. Blah.
Adept power is nifty, however, in the event that you are stuck in total darkness-this coupled with Motion Sense(which is just awesome), can essentially reduce full darkness to -2 and you need no vision mods for it. (And even someone with partial vision loss-the -3 version, is still at a -6 in Full Darkness.)
It still is a bit odd that someone needs to be TOTALLY in the dark to benefit-and can even end up *the same*. In the event of say, Smoke/Thermal Smoke, a person with Normal vision, the Blind-Fighting Power and Motion Sense gets a -2 total-since the Blind-Fighting power apparently only works in full darkness, but Motion Sense can work. The totally blind/Blindfolded guy can also get a -2, with the same two powers, just because he's...totally blind. (I'm guessing the totally blind guy does not suffer an extra -4 from Thermal Smoke, since, well, he's always assumed Total Darkness.)
Which also makes me wonder how they stack. A blind guy I assume always uses the Full Darkness modifier. But does a -3 suffer from Glare? Does he stack the thermal smoke? I hope not, in that case I certainly WOULD have the -3 to sight be worth a lot more BP. Or is this just a case of using the ''single worst vision mod'' (ie, someone with -3 partial vision loss in Thermal Smoke would just be at a -4.) I'm guessing/hoping it's the latter. (I have some bad memories of a game-and damned if I remember which one, but I remember this specifically-that a blind person ended up sometimes better in a lot of situations than someone who was almost blind. Which none of us ever understood.)
As for stacking mods, I DO know and expect multiple different mods to stack-IE, someone totally hidden in thermal smoke, yeah, I can easily see that being supposed to stack.