People remembering your handle is persistent, and people remembering if they had good or annoying interactions with you is persistent reputation that exists in the minds and interactions between different people. These are things people naturally do. If people don’t recognize your name and see it come in a trusted spot they just don’t trust you.
How tech breaks this is deprioritizes the people in the interactions. Instead of sending messages you use a “like” button to be intelligible to the platform. You don’t see the people putting stuff on your feed, it gets fed to a timeline that cuts it off from all context and atomizes it for your consumption. It’s the UI/UX that drives this. Even compare Reddit and HN with old forums. On forums like 25% of every post is just static bits of self-expression. There’s a PFP, the username is bigger, there’s often a big signature block. All of this makes the peoples’ posts feel like a person talking to you rather than text blocks that happen to have a tiny username and timestamp on it.
Edit: to clarify: You aren't your handle, because it can be taken away from you, can be injected, blocked, overridden, etc.
My technical rambling then went on about how or when we can make this "handle" decentralized so it cannot be taken away from you. Hard. As proven in practice. Almost impossible.
My name is maintained by a government. It is a "handle" that could be taken away too, but is governed in lots of rules, systems and regulations. My face (an extension of my DNA, I guess) is decentralized and owned by me: its the only handle that afaik no one can take from me.
So in social interactions, you're right: reputation, bound to "me", my face, my DNA is all that matters. But online we don't have this. The closest we can probably get is "my name", controlled by governments.