See: https://forum.inaturalist.org/t/how-to-curate-nomen-dubium-taxa/19118
And see: https://www.inaturalist.org/flags/642741
I still haven’t received a satisfying answer for this question, but what are the rules for curating the nomen dubiums. Here’s what has changed since the first forum discussion. Orthoptera Species Files (OSF) formerly listed its taxa in the following order: invalid taxa (ex. nomen dubium, nomen nudum), species, subspecies, and synonyms. It was under my impression than any taxa listed that started out with “nomen” instead of “species”, it is not acceptable for iNat, and I was inactivating such taxa.
When OSF transitioned to its new website last August, it changed its format. Nomen dubiums are now considered “valid” names and these taxa are integrated alphabetically within well-recognized species. Nomen nudum have to be manually typed in the search bar to find since it is not listed within the family tree. In summary, the OSF doesn’t clearly separate nomen dubiums from regular species, thus implying they’re valid and acceptable for iNaturalist. In which case, I would have to go back and reactivate some taxa I’ve closed in the past.
Here’s an example of the old vs new OSF:
Nomen dubium (old): Listed separately from species, see S. calcaratus
http://orthoptera.archive.speciesfile.org/Common/basic/Taxa.aspx?TaxonNameID=1132145
Nomen dubium (new): List integrated with species, see S. calcaratus
https://orthoptera.speciesfile.org/otus/841460/overview
Nomen nudum (old): Listed separately from species, see C. torulosinota
http://orthoptera.archive.speciesfile.org/Common/basic/Taxa.aspx?TaxonNameID=1101412
Nomen nudum (new): Not listed on genus page, but does have a taxon page
https://orthoptera.speciesfile.org/otus/807565/overview
https://orthoptera.speciesfile.org/otus/807576/overview
I think it would be a great idea to clarify iNat’s standings on these matters, and list these rules in the curator guide. I think nomen nudums will be easy to deal with (just don’t add them, and inactivate those that are), but we kind of hit a gray zone with nomen dubium with OSF’s new system.