This is how people are solving the soy-TOFU problem (Trust On First Use). Not so much as nostr has a problem with new users needing to trust other nostriches, but they can't carry-over their identity and credibility from other platforms. Yes, its a soyboy bitch about nostr, why should you have instant credibility on another platform with no work? But its a valid point that people shoukd have a way of authenticating themselves in nostr without posting their new identity on the old platform (because of censorship by the platform).

So how do you do it?

Rather than promoting your own new identity, demote imposters. This is possible by associating yourself with a bitcoin wallet address that you post on both platforms. This way, you are saying on either platform "I accept donations at this address" without explicitly indicating you are moving away from the compromised platform. If, on nostr, you can include a message signed by the wallet's private key indicating that your npub also controls that same wallet address, then you have proof positive on nostr that you are who you say you are.