Experiments on the Alcator C-Mod and JET tokamaks with identical values of nondimensional variables at the pedestal top are expected to have the same local plasma transport for a ratio > 4 in absolute size and thus can help to clarify other effects in pedestal formation. At the high and low fields (7.9 T, 1.4 T respectively) involved, natural-density H-modes on C-Mod were of conventional ELM-free type, while those on JET were steady but with only small, sporadic ELMs. Nevertheless, they remained close to a common regime and a good non-dimensional match at the edge was achieved for highest C-Mod densities spanned. Pedestal profiles were measured with a fine-resolution edge Thomson scattering diagnostic on C-Mod, plus a new high-resolution (HRTS) system on JET. Electron temperature widths on JET were estimated to lie between scaled C-Mod levels and somewhat broader fitted shapes. Density pedestal widths, however, were reliably found to be proportionally broader than on C-Mod, signalling an influence other than plasma transport in their formation. Edge particle sources were modelled for both devices with the 1-D kinetic KN1D code and corroborated for JET using the 2-D fluid-plasma / kinetic-gas EDGE2D-NIMBUS suite. Overlaying normalised profiles of ionisation rates suggested density pedestal thicknesses were at least partly related to neutral-particle penetration. Such dependence implies their scaling is not Kadomtsev-like for the collisional, low-normalised-pressure conditions investigated, so precluding unambiguous scans versus dimensionless variables like normalised Larmor radius.