Apparently, back in 2023 I put some time into researching why opting out of community ID was added and how it was supposed to function. (tl;dr: It was added in 2014 at the same time as the concept of community ID, probably because iNat staff had some doubts about whether community IDs could always be trusted.)
https://forum.inaturalist.org/t/opting-out-of-community-taxon/38062/147?u=rupertclayton
If I was in a dogmatic mood, I might say that the community ID experiment has been running for nearly 12 years and has proven successful. So, it’s time to discontinue the opt-out option.
I don’t think that’s going to happen, and I think it might push a lot of people to leave iNat, so my recommendation would be to ignore opt-out observations if they annoy you. If they’re contributing to incorrect data, you should add a correct ID, which will usually change the CID even though the observation ID remains the one selected by the observer. There are also DQA fields that may be applicable.