> Marx is dealing here with the production of use-values,
> abstracted from the capitalist form of production.
Bingo! This is exactly the point I wanted you to note.
Marx's concepts should be understood in the context of the particular level of abstraction on which he's operating at each particular point of his presentation. If the context is the examination of commodity production in general, then productive labor will be that labor productive of values. If the examination of capitalist production, then productive labor will be that labor productive of capital. Etc.
Of course, *that* defintion is not *directly* applicable to the capitalist mode of production. But note that "not directly applicable to" does not mean "not applicable at all." It means that this determination is a piece of the totality that will be modified as you look into the more specific aspects of the phenomenon.
Now, capitalist production is an essential element of a capitalist social formation, but it is not its totality. When we take into consideration the reproduction of wage workers (something outside of the C-M-C' circuit proper) or when we incorporate the side of wage workers in our understanding of how a capitalist society functions -- not workers as mere passive instruments of capital, but as human beings capable of resistance and struggle -- how should we modify our notion of productive labor? Or should we not? Should we stop the progression at the point where Marx left it? Again, alluding to Marx's method is not irrelevant, because it allows one to see how each of Marx's apparently contradictory statements are rather complementary.
Oh and let's make a deal: You stop addressing me with unearned familiarity and I'll seriously reconsider my current impression of you as a full-of-shit arrogant prick.