I have a friend who operates a therapeutic riding center for people with mental disabilities. This alone is fascinating and she primarily works with children. However she is also qualified to work with the Wounded Warriors Project and has a great group of retired soldiers who may be physically impaired, or suffer from PTSD or other mental condition.
What started her passion for this is her now teenage daughter who was born with genetic selective mutism. The daughter physically cannot speak around strangers. As such, in public, or when non family members are around, the daughter can only communicate by body language and expressions. This has made the mother sensitive to BL and expressions out of necessity.
What's interesting is that in private, at home, the daughter can talk normally just like anyone else. The mother told me in a discussion that what is wonderful about this is that she can quiz her daughter about things that happened earlier that day.
She will ask her daughter questions like "When you pulled this expression, or made this motion or tried to indicate this, what was going through your mind? or what were you feeling?" And the daughter can freely answer her.
The mother uses this information to better understand the children she works with. Like with children who might be non-verbal autistic or other conditions that make them unable to speak. She can compare the BL and expressions against her daughters answers to similar expressions to better understand what the child may be communicating.