The strategy applied in the structure refinement of accurate single-crystal neutron diffraction data for pseudo-centrosymmetric proton conducting systems can often be decisive. The application of a combination of judicious symmetry constraints and symmetry-lowering procedures can expose the likely route for proton transfer, otherwise not revealed by a disordered centrosymmetric model involving partially occupied H-sites, e.g. O-H/2...H/2-O. This procedure will be illustrated for the simple case of an apparently disordered structure which has recently appeared in the literature. The structure was stated to involve an H3O2- ion lying across a centre of symmetry. Use of the strategy suggested here resulted in an ordered H2O...OH- arrangement, involving a quite reasonable O-H...O hydrogen-bond geometry, and low correlations between all parameters varied in the refinement. interestingly, it is shown that the proton can be placed equally successfully on either side of the central H-bond, implying that the entire crystal comprises extended regions (domains) which are dominated by one or other of the H-bond orientations, i.e. one or other of the non-centrosymmetric structural enantiomorphs. The size of these domains must be well in excess of the coherence length of the diffraction experiment. indeed, a single domain can, in principle, extend across the whole crystal.