The phrase "a man of his word" is a standard phrase. "Word" sometimes mean "promise." "You have my word" means "I promise." "A man of his word" means "a man who keeps his promises." The speaker is making a bitter joke. The phrase "a man of his subtext" is not a standard phrase. She is making a creative variation on the standard phrase. A "subtext" is a hidden meaning is intended to be understood by some people but not others. She is attacking somebody. She says he does not keep promises--not the actual words he speaks. She says that his followers understand his hidden meaning, which is different from the meaning of the words he speaks. He does keep those hidden "promises."

He doesn't say what he means directly or explicitly, but there are clues about his intended meaning if you listen carefully.