Recently one of the most spanking popular blogs labeled a story by a very popular author as F/m. The characters in the story were an adult woman and a college age man. I commented that I thought the story was mislabeled and that the correct label would be F/M. My objection was dismissed as she believes the lower case letter indicates the spankee is submissive. Horseshit.
This subject was extensively argued on the defunct ASS/SSS newsgroup 20 years ago. I thought it was settled long ago. The largest collection of spanking lit, The Library of Spanking Fiction, uses the second letter to indicate the age of the spankee. In that the spankee is always the second letter, be that person actually submissive or not, there is no need for it to serve any purpose than indicating if the spankee is an adult or not.
I get on my high horse about this as I would not ever want anyone to think of Bacall paddling me as a submissive or treating me as a child. And I sure as hell do not treat her as a child when I put the wood to her. It’s M/F and F/M for us and it makes a difference to us.
Our Bottoms Burn 
The lower case means a child. So F/m would indicate an adult female spanking a male child. F/M indicates an adult female spanking an adult male.
JGH57
Exactly. I recognize your sig from LSF