I am reminded of Sartre's famous key-hole observer suddenly discovering himself being observed, suffusing the subject with shame and a kind of objectifying "mortification."
I know this is not what you had in mind, but I raise it in order the reintroduce the missing aspect of awareness and psychology in these inanimate "particle" observers, these Disney "atoms" with cartoon eyes.
While I too am fascinated by questions of symmetry and measurement and value metaphor, I simply fail to understand the definition of "observe" here. It is either metaphorical or collapses a meaningful distinction to little avail.
Why is "observe" an accurate description of this relation between particles? Certainly, we can might say that a "measurement" takes place in the purely physical sense that information is transferred between particles. Such a transfer is not necessarily reversible. I believe it is, in fact, physically irreversible. So these perspicacious "particles" do not necessarily observe one another, at least not with equal "accuracy."
But again, I can only take this as useful metaphor.The physical, particulate information has syntax, but no semantics. I see no gain in a massive, gratuitous reduction of what we normally call "observation" of an object by a "conscious subject" to a physical, mechanical relation between two objects under the same term.
And I tend to agree with the unpronounceable commenter that the subject cannot be an object to itself, just as we can never actually see our own face, only its reverse. While we can approach the imaginative ideal of subject-object identity, the distinction can never be meaningfully collapsed. They remain, as it were, inside-out or chiral to one another.