My point was that the paper that defines the range boundary as the river explicitly makes the point that appearance is not enough to distinguish the species here. So someone making an ID based on appearance is directly contradicting the taxonomic source that iNaturalist has chosen to use. They are not providing evidence against the taxonomic source, they are just saying that they disagree with it.
That’s a perfectly fine discussion to have, but it should be had (according to iNaturalist’s stated policy) outside of the scope of the specific observation, as @reuvenm explained above.
Note that for this particular case the discussion is not about subspecies but about species, which removes the option of just identifying to the species level.