What do trifling, petty and picayune mean when describing a person? According to dictionaries I looked at, they all mean worthless and trivial, but then following sentence does not make sense to me. I also found picayune has a meaning of "carping or prejudiced", which I still can't fit it into the sentence.
Can someone explain what do they mean exactly in this sentence? As far as I understand the logic of the sentence, the words picayune in the sentence should have a meaning similar to "contrary to the rules" but I just can't find any definition similar to that.
English teachers are notorious for being picayune(trifling, petty); however, the English language is so nuanced and sophisticated that often such teachers are not being contrary but are only adhering to the rules.