With regard to many of these photographs, it was History which separated me from
them.  Is History not simply that time when we were not born?  I could read my
nonexistence in the clothes my mother had worn before I can remember her.  There is a
kind of stupefaction in seeing a familiar being dressed up differently.

Barthes, Camera Lucida (1981), p. 64

Roland Barthes's writing is distinctive for its play between methodological approaches: consider Mythologies, for example, which is both a scholarly, structuralist analysis of mythologizing and a celebration and creation of the diversity and accessibility of myths in culture. This passage from Camera Lucida similarly reflects this kind of play, or pleasure: it is an analysis of a phenomenon (of "nonexistence," of "stupefaction," of "History") that is at the same time an occurence of that phenomenon. Barthes recounts an encounter with History, but the writing of the encounter is itself an encounter, and the language he uses is determined by the effects of this encounter. Writing about difference and oblivion, his language differentiates and obliviates.
The use of the term "History" itself reflects this incorporation of content into form. Barthes has experienced a confrontation with something outside himself, something whose existence depends on his non-existence, something that requires his subjectivity in order to be recognized but is simultaneously the end to individual subjectivities. Thus in writing about it, Barthes is reverent: capitalizing "(H)istory" brings all these issues to the fore, for it is clearly Barthes-the-writer who chooses this capitalization, yet doing so is an attempt to reproduce a thing that is wholly not-Barthes. Though this concept ultimately is "that which I [Barthes] will call 'history'," the choice to introduce it as simply "History" is a move to give up this authorial authority, to move from having the term as his property to a state of propertylessness (or even of being property to the term, depending on how much agency we really want to assign to this force).
A second lingual marking of this play in Barthes is his use of personal pronouns. This passage about the emergence of difference out of a difference of context makes use of context to differentiate between pronouns that supposedly refer to the same subject. Consider the introduction of "we" in the second sentence, a question; following the "me" of the first sentence, this would seem to be a generalization, an extension of an invitation to the understood "you" of the interrogative to reflect on this phenomenon as if it was the property of all of "us" (or, following the dicussion in the previous paragraph, the property that belongs equally to none of us). Yet the "me" of the first sentence is specifically a "separated" subject, isolated and observant; and the question is immediatley followed (answered?) by an "I," a very personal "I" that confesses its uncertainty and maternal affection. It would seem that this "we" is a joke, an invitation to a place that does not exist.
Even in the pronouns "I" and "me," there is a play of representation going on. The difference between subjective and objective case is here realized to its fullest: "me" does not exist, is forced into nonexistence by an external, separating force whose supreme agency reduces subject-Barthes to object-"me"; however, the working of this force depends on its recognition, on a subject-"I" to possess and study the photographs in which "History" can have this power. Thus the nonexistence of "me" depends on the external/authorial existence of "I" to recount this encounter with the product of its consciousness.
Is there any wonder, then, that the last sentence is in passive voice, that neither "I" nor "me" is stupefied or sees, but merely "stupefaction" and "seeing" exist? This is speech that at once both sees and is stupefied by what it sees. Though the context produces the conclusion as being about Barthes's mother, that it is she who is "familiar" and yet "different," the play in the text suggests another reading: it is "I" that is familiar, and what is stupefying is not only seeing "I" objectified into "me," but also "I" not-seeing the non-existence of "me," seeing itself dressed by "History" in the garb of oblivion.