Chrisma is the noun of the verb chriō, to smear. It is not the ceremony of anointing and not the feeling of being anointed. It is the ointment itself, the oil that got on you and stays on you. Yochanan builds a deliberate pun on it: you have received the chrisma because you belong to the Christos, the Anointed One (1 John 2:20, 27). The Anointed shares His anointing. That is the whole logic of the word.

In the Hebrew world underneath the Greek, oil smeared on a head installed prophets, priests, and kings. The oil transferred function and standing, not information. So when Yochanan says the chrisma teaches you about everything and you have no need that anyone should teach you, he is not flattering the reader's intelligence. He is saying the promise of Isaiah 54:13 has landed: all your children shall be taught by YHWH. The abiding presence of the Ruach is the anointing, and the anointing is HaShem doing the teaching Himself, from within, which no human office can replace and no human office can revoke.