It is conceivable that a language distinguishes the following meaning-structures in the morphology of its reciprocals:
A acts on B and B acts on A > A and B act on each other
A acts on B or B acts on A > A or B act on each other_disjunctive.
One could even imagine, then, that partial negations also could fit into this:
A but not B act on each other_disjunctive.
This could be done by differential case or by some marker that is entirely separate from case.