Presumably COTE comes from Common Teal, the name the species had while lumped with the Eurasian Teal. If this was a genuinely used banding code then I think there is no issue, as its one of several antiquated common names for the species (provided you’re willing to accept banding codes as common names, and I guess the issue that even if restricted in use to the ABA area it is a slightly different taxonomic concept). If it wasn’t, it should probably be removed. Either way this isn’t a bug, just a disagreement over a user submitted common name. Banding codes aren’t officially supported on iNat or anything, many people just add them as common names for various species.
Understood; even if COTE was the proper code for Common Teal, that name that hasn’t been used since 1973. There is a legit code conflict presently, which isn’t nothing. I can’t say how many people have either noticed this or care; I would wager it’s at least one more than the number of people who would notice if it were updated to the present set of codes. Codes have been updated for more recent lumps and splits, so I suggest this one ought to be as well.
A conflict is an issue if you’re creating what’s supposed to be an authoritative list of unique names (like a single set of banding codes). But common names on iNat are a collection of many, often times non-unique, names for organisms. The common name “Elk” is listed for both Alces alces and Cervua canadensis, as it should be, as that word is used by different people to refer to both those species. Common names on iNat are descriptive, not prescriptive, so I don’t think avoiding conflicts or keeping up with current taxonomy are very strong arguments for delisting one.