My teacher put S.F. next to one of the last sentences in my paragraph that was part of my essay. My sentence was "A remarkable man he was for being so caring." What does S.F. mean?
SF means sentence fragment. The teacher thinks that your last sentence is not a complete sentence.
The way you wrote the "sentence" it is actually a participle phrase.
The was does not function as a verb the way your wrote it. He was describes the remarkable man. It does not describe an action or a state of being.
The sentence could be reworded He was a remarkable man because he was so caring.
So SF means that sentence fragment. SF means that you have not written a complete sentence.