Following my question here I am still unsure if it is a 'hard and fast' rule to italicise thoughts.
My preference is to use normal quotation marks, so that if a person is thinking in a dialogue situation or description, all the text appear normal. I follow British style.
"Are you Ok?" the teacher asked.
"Damn," John thought as he tried to cover his wounded hand.
"Are you OK?" the teacher asked again.