This addendum establishes formal mathematical correspondences between the DSM-861 spectral manifold and structures appearing in Monstrous Moonshine and the Dedekind eta function.Three precise connections are identified. First, the geometric commensurability defect δ = N/G−12 = 861/72 − 12 = −1/24 is exactly the exponent in the eta function prefactor q 1/24, and theEuler-Maclaurin Casimir residue |ε| = B2/2! = 1/12 satisfies |ε| = 2|δ| (corrected from the originalequation which incorrectly stated |ε| = |δ|/2). Second, the June 2026 Dehn twist proof establishes that η(τ + 1) = exp(iπ/12)η(τ) is the modular identity that directly produces the −1/12 anomalous dimension in the Navier-Stokes regularity proof—so the Moonshine connection is not merely analogical but is the operative mathematical mechanism. Third, the specific Moonshine coefficient 196884 appears explicitly in the DSM-861 quality factor: ∆j = 196884exp(−π√163) = 7.4993 × 10−13. The coefficient 196884 is the first non-trivial coefficient of the j-function j(τ) =q−1 +744+196884q+..., which by McKay’s observation equals 196883+1, where 196883 is the dimension of the Monster group’s smallest faithful representation. This is the precise Monstrous Moonshine link for DSM-861: the j-function residue at the Heegner point τ∗ directly encodes a Monster representation dimension. The paper does not claim direct equivalence between DSM-861 and V♮ (which has c = 24 and Monster symmetry); DSM-861 has c = 1 and C72 symmetry. The correspondences are genuine and precise but operate at the level of shared modular structures, not group isomorphisms.