The node address is indeed the way to identify an entity on the blockchain, because it has an associated private key that only that entity can use to prove that it is the source of transactions and other things.
But there are several ways in which this identification can be enriched, using streams. Either the node itself can publish self-identifying information from that (publisher) address, or else other entities can publish information about that address, for example by putting that address in the key of stream items.