It isn't clear whether the purpose of the anti-silvering compound in Microdol-X was to avoid dichroic fog, improve sharpness by inhibiting physical development, or reduce sludging (I suspect it had more to do with sludging). Ilford's Perceptol (similar if not identical to Microdol) doesn't have dichroic fog problems. In the case of Microdol/Perceptol (which are based on D-23) I would not expect the additional solvent effect from the ~30g/L NaCl to cause dichroic fog problems. I think for that you really need a more powerful solvent (like the thiocyanate in DK-20 for example) and/or an even lower pH than Microdol.
In a high pH developer like Rodinal which is essentially non-solvent to begin with I can't see how adding 30g/L NaCl would provoke dichroic fog.