“for Marx there is no subject of surplus-value, unless one fetishises the appearance of capital as the vital subject of valorisation, as is the case in the developed forms of capitalist abstractions such as financial capital (but also on the more ‘immediate’ level of commodities and money).”
— The Capitalist Unconscious: Marx and Lacan by Samo Tomsic
This is simply mistaken. Either Tomšič is unfamiliar with the Marx passage on the Subject, which is doubtful, or he is unfamiliar with its source, again doubtful, or he has never put the two together, more likely.
The Marx passage:
It is constantly changing from one form into the other, without becoming lost in this movement; it thus becomes transformed into an automatic subject. If we pin down the specific forms of appearance assumed in turn by self-valorizing value in the course of its life, we reach the following elucidation: capital is money, capital is commodities. In truth, however, value is here the subject of a process in which, while constantly assuming the form in turn of money and commodities, it changes its own magnitude, throws off surplus-value from itself considered as original value, and thus valorizes itself independently. . . . But now, in the circulation M-C-M´, value suddenly presents itself as a self-moving substance which passes through a process of its own, and for which commodities and money are both mere forms. But there is more to come: instead of simply representing the relations of commodities, it now enters into a private relationship with itself, as it were (Capital, I.iv).
Marx is not fetishizing the value form of capital. Rather is he disavowing (1) that the subjects to the exchange are subjects; (2) that the surface form of appearance, “the commodity,” is subject; and (3) that the money form is subject. It is instead the value form of capital that is subject, not “labor-power” as Milner and Tomšič suggest and perhaps Lacan implies. Marx here historicizes and socializes Hegel’s grasp of the Subject from Phenomenology:
Further, the living Substance is being which is in truth Subject, or, what is the same, is in truth actual only in so far as it is the movement of positing itself, or is the mediation of its self-othering with itself. This Substance is, as Subject, pure, simple negativity, and is for this very reason the bifurcation of the simple; it is the doubling which sets up opposition, and then again the negation of this indifferent diversity and of its antithesis [the immediate simplicity]. Only this self-restoring Same-ness, or this reflection in otherness within itself — not an original or immediate unity as such — is the True. It is the process of its own becoming, the circle that presupposes its end as its goal, having its end also as its beginning; and only by being worked out to its end, is it actual. Thus the life of God and divine cognition may well be spoken of as a disporting of Love with itself; but this idea sinks into mere edification, and even insipidity, if it lacks the seriousness, the suffering, the patience, and the labor of the negative (Phenomenology §§18-19).
This is not a feature of language, not of signifier and signified, but of the commodity, both its value form and its surface forms of appearance.