Face tagging doesn't correctly auto-complete hierarchical keywords.
Suppose I have two keywords, Family > Peter and Friends > Peter. In the Keywording panel, when I start typing "Peter", LR suggests both keywords and lets me choose:
But the person box above a face rectangle provides two choices, unqualified by the parent keyword:
It doesn't matter which you click on, you'll always get Family > Peter.
And you can't use the Parent > Child or Child > Parent notation -- see this bug report: http://feedback.photoshop.com/photosh...