I have recently gone through my entire catalogue of family pictures (over 60k) and tagged my family members in each picture. I love how face detection works in Lightroom, is great, but I think it would be even better if users could have the option to enable or disable duplicates on the same photo. Once I have confirmed that, for example, my sister is in this picture, I would like Lightroom to stop suggesting that other people are my sister and instance suggest a different person. I think this would speed up the process of tagging people a lot! I know people can be reflected on mirrors or an image can be a collage of several pictures, but I would say that in 98% of the cases one person is not gonna appear twice in the same picture and if it does a single tag would be sufficient to find that picture again.