After this feature request along those lines was closed in July 2019 (https://forum.inaturalist.org/t/create-a-way-to-flag-duplicate-observations-and-remove-rg-status-from-the-extras/201), I sent this reponse privately, but I’ll post it here (lightly modified :)
In a lot of cases the observations shouldn’t even be merged though. One just needs to be deleted. I would estimate in >95% of instances folks do not follow up on their duplicates or other data quality issues. This will only be a very, very minor help.
Duplicates are a huge pain in the butt for identifiers. Anything that makes the identification process slower and more frustrating is a major data issue.
We’ve been flagging them for years. The “acceptable” observation is the one that is oldest or isn’t flagged.
I plan on continuing to flag duplicates as I see them in order to remove them from the Identify pool. This will continue to make the flags page unwieldy and difficult to manage.