It is a moral incongruity for blessing and cursing to come out of the same mouth. The neuter singular articular adjective is a common way of presenting a quality. Negative answer expected. Common in Paul and characteristic of the diatribe. Emphatic position of this verb.
Actions speak louder than words even in the case of the professional wise man.
This is a condition of the first class. Wisdom is essential for the teacher. Boasting arrogance disproves the possession of wisdom. Lying against the truth is futile. All true wisdom comes from God.