Is this a new user? If so, maybe let them know that you’re subscribed to taxon X or identify in area Y, so their observations will appear in your ID feed. It may be helpful to point them to your ID map to show that they’re not being singled out (URL borrowed from topic: Your top 10 most identfied).
If it’s a seasoned user, would agree with @marina_gorbunova that they can block you, if they want.
It’s absolutely normal for a small handful of people to do most of the IDs in an area, so I don’t see any problem with you being a top identifier for specific people in your area.
Edit: If there aren’t too many identifier URLs to bookmark, it’s possible to exclude one or more specific observers by tacking this on to the end:
¬_user_id=annoyed_observer
Softer option than blocking, maybe?