Mark repeatedly uses supernatural recognition to create dramatic irony. Demons know who Jesus is while crowds and disciples struggle to understand.
Jesus silences the spirits, preventing hostile supernatural witnesses from controlling the disclosure of his identity.
The Old Testament can use son language for Israel and the Davidic king, so 'Son of God' cannot simply be treated as a lexical synonym for deity.
Mark progressively fills Jesus' sonship with greater significance through the Father's declarations, the beloved Son parable, heavenly authority, and the Passion.
The spirits do more than acknowledge Jesus' power: they fall before him and identify him as the Son of God. Jesus does not deny the identification; he commands silence.
This continues the recognition motif introduced in Mark 1:24.
The record is Supporting because the title requires interpretation from the whole Gospel.
Its significance is narrative: beings from the spiritual realm recognize an identity that Mark's human characters have not yet adequately perceived.
The spirits fall before Jesus and identify him; Jesus strictly orders them not to disclose him.