That common name technically best applies to certain forms of the species (and likely part of P. aurifer prior to being split) and not the entire species. This is a case of a species holding several common names, and the default name on iNat was selected due to being the most appropriate (or rather least inappropriate) throughout its range. The other common names are still included on the taxon for searches.

These are also noted on the Polistes Common Names (And Other Curiosities) journal entry.

Are wasps like birds where common names are officially determined by an organization, or like most other taxa where the most "proper" common name is that one that's actually used most often?

Wasps and other insects become rather difficult (especially in cases like this where several valid names are in circulation). There are a few organizations, such as ESA, that work on some form of standardization, but many species (including this) aren't in their database. There are also names used by the CDC, which exclusively uses dark paper wasp (also used in references from Cambridge University Press, including Robinson's Handbook of Urban Entomology). Typically, even when organizations determine proper insect names, the vernacular often lags way behind. As noted, the current name has been curated to the default as it's the least wrong throughout its range (and as the split of P. aurifer from P. fuscatus changed how a few names apply).

I see bugguide is already using Northern Paper Wasp. So, are all in agreement to change the name here to Northern too? In the event not, why is it named Northern on bugguide currently?