I was not advocating that we should use regional sources (it’s more that many national and global authorities provide no common names). I do understand that we need to guard against duplicating common names just because each source is only considering a limited context.
However, my point was more general. @bobby23 seems to be saying that if a source that we consider reliable attests to the same common name for both the parent species and the nominate subspecies it’s acceptable to use that common name for both taxa in iNat. I support that approach but it seems to contradict the policy that you cited:
Going back to the example I gave, all three subspecies of Dichelostemma capitatum do occur in California, so when I use Calflora as an example of the same common name (Blue Dicks) being applied to parent and child taxa the duplication isn’t happening because the source has limited scope. It’s because there is no separate common name for Dichelostemma capitatum ssp. capitatum.
If there was a unique common name for this subspecies (which accounts for about 80% of observations for this species) we should certainly just use that and avoid duplication. Without the option to use a unique name, it seems it’s more helpful to the many iNat users who have observed ssp. capitatum that they’re aware of its common name than that we pretend it doesn’t have one.
In my view, the bulk upload issue that @treichard mentions could be fixed in code. Where parent and child taxa have the same common name, the upload tool could default to map that common name to the parent taxon. If duplicate common names don’t have a parent child relationship (e.g. “ice plant”) the photo tag should not generate an ID.
Finally, I think the curator guide is inconsistent when it first says
If a species has no common name in usage, please don’t make one up.
and then a paragraph later has this advice
Instead, try to choose unique common names like “Coke Classic” and “Coke Zero.”
How do we “choose” unique common names when those don’t actually exist?