Armon on Nostr: Question, I see "attacks" on how biden used his twitter to post his letter about ...

Question, I see "attacks" on how biden used his twitter to post his letter about dropping out of the race. People said "how do we even know that was him. He should have a private key to sign his communications like on Nostr" ... Even if he had a Nostr... Why couldn't someone run his or any nostr account? Nor if i started to impersonate someone, would there be a way for people to get me banned. #asknostr. Trying to learn here please educate me