The Gnani will neither talk too volubly like shallow persons nor keep complete silence. He will talk as much as is necessary but no more.
Silence really means keep quiet in controversial discussions because one does not know what anyone has in his mind and without semantic analysis it is all useless, so silence is better.
In pursuit of truth silence means thinking constantly of the formless as against universe. Word and thought always imply duality, the object, whereas the subject, formless witness or consciousness is beyond both word and thought.
The physical silence practiced by yogis, is a sign of their ignorance, because they are thinking of the tongue and lips, i.e. body and not of the formless witness, which consciousness. However it is useful to those who are not seeking truth as a discipline. Yogic silence was intended only for the ignorant, who are unfit for path of wisdom.
Consciousness is wrapped in the meaning of words. Semantics aim at clarifying meanings but AUM ultimately shows you that all words are futile because they cannot express the ultimate nature of anything: Silence alone does this.