Upon thermal annealing at or above room temperature (RT) and at high hydrostatic pressure P ~ 155 GPa, sulfur trihydride H3S exhibits a measured maximum superconducting transition temperature TC ~ 200 K. Various theoretical frameworks incorporating strong electron–phonon coupling and Coulomb repulsion have reproduced this record-level TC. Of particular relevance is that experimentally observed H–D isotopic correlations among TC, P, and annealed order indicate an H–D isotope effect exponent α limited to values ⩽ 0.183, leaving open for consideration unconventional high-TC superconductivity with electronic-based enhancements. The work presented herein examines Coulombic pairing arising from interactions between neighboring S and H species on separate interlaced sublattices constituting H3S in the Imm structure. The optimal value of the transition temperature is calculated from TC0 = Λe2/ζ, with Λ = 0.007465 Å, inter-sublattice S–H separation spacing ζ = a0/, interaction charge linear spacing = a0 (3/σ)1/2, average participating charge fraction σ = 3.43 ± 0.10 estimated from calculated H-projected electron states, and lattice parameter a0 = 3.0823 Å at P = 155 GPa. The resulting value of TC0 = 198.5 ± 3.0 K is in excellent agreement with transition temperatures determined from resistivity (196–200 K onsets, 190–197 K midpoints), susceptibility (200 K onset), and critical magnetic fields (203.5 K by extrapolation). Analysis of mid-infrared reflectivity data confirms the expected correlation between boson energy and ζ−1. Suppression of TC below TC0, correlating with increasing residual resistance for < RT annealing, is treated in terms of scattering-induced pair breaking. Correspondences between H3S and layered high-TC superconductor structures are also discussed, and a model considering Compton scattering of virtual photons of energies ⩽ e2/ζ by inter-sublattice electrons is introduced, illustrating that Λ ∝ ƛC, where ƛC is the reduced electron Compton wavelength.