For bulk MoS2, introduction of S-vacancies is known to enhance (electro)catalytic activity for HER, where the basis for enhancement appears to be lattice strain that, in turn, translates to stronger affinity of sulfide sites for H atoms. While a similar effect conceivably could be operative here, an attractive, albeit speculative, alternative explanation is that exposure of initially octahedral molybdenum ions due to sulfur loss from the cluster opens up the system to Mo-hydride formation, with H2 then being formed via reaction with a sulfur-bound proton -either based on PTM-ligated sulfhydryl or H2S.