Update:
New project containing observations of 453 users (so far) that have opted-out (in their profile):
https://www.inaturalist.org/projects/user-has-opted-out-of-community-taxon-collection
For excluding these observations, append one of these filters to your search URLs:
¬_in_project=user-has-opted-out-of-community-taxon-collection ¬_in_project=153984
BTW, by substracting from the 1st project all observations in this 2nd projects, remain only a few observations (26 so far), for which the observers have opted-out, but only for these observations, not for all observations. This illustrates how minoritary are the cases of opting-out only for some observations.