what is the best approach to removing a photo or document from familysearch memories that someone else has posted to the wrong person ?
Your question will be forwarded to a Memories team for review and assistance. You may be contacted by that team if they need more information.
I would consider doing two things. 1. contact the person who incorrectly linked the photo and see if you can agree with them as to the validity of the linkage. If you get them to agree to remove it will minimize and future conflicts that could arise. 2. if you cannot contact then you can unlink the photo so that it does not appear in the memories of the wrong individual -- see the linked article below that explains how to unlink a photo or document.
If you know who the correct individual in the photo, you can add a tag to the correct ID number, and explain why.