III.D27 — Functional Equation Involution J

The involution J(s) = 1 − s̄ on the split-complex s-plane. Exchanges B-lobe and C-lobe: J swaps e₊ and e₋ components. The functional equation ζ_τ(s) = C(s)·ζ_τ(J(s)) is the bipolar symmetry statement.