MY NEW ADDRESS:
-----BEGIN BITCOIN SIGNED MESSAGE-----
Hi. This is Marvell1. Today August 10 2021
I want to proof my new BTC address: bc1q0h35js5pm2qrnfx3a44jv4funs0fkqqhd3dlq8
-----BEGIN SIGNATURE-----
bc1q0h35js5pm2qrnfx3a44jv4funs0fkqqhd3dlq8
IF9LOCOd2qFizu++ZzZOwnNn0ciYjWHm21K04BlslEypReoY9MM9hqdGvkx0V1CFWTIgagtfQXrkJBZwezon0ic=
-----END BITCOIN SIGNED MESSAGE-----
Think about what you are trying to do.
Marvell1 wrote a message 4 years ago saying that their signing address is 1NNSoJsWABSiqftBVWze6HUFRFtaBkZy4G. Now, a person claiming to be Marvell1 is saying that they want to use another address for signing.
How does someone know that Marvell1 truly wants to use a new address? Marvell1 signs a message saying that they want to use the new signing address. Without a signature, the message can be changed.
How does someone know that the person changing the address is the true Marvell1? The message is signed with the original signing address. Presumably, only the true Marvell1 can sign using that address.
In short,
-----BEGIN BITCOIN SIGNED MESSAGE-----
Hi. This is Marvell1. Today August 10 2021
I want to proof my new BTC address: bc1q0h35js5pm2qrnfx3a44jv4funs0fkqqhd3dlq8
-----BEGIN SIGNATURE-----
-----END BITCOIN SIGNED MESSAGE-----
On the other hand, what you have done (sign messages with both addresses) is sufficient in practical terms because while someone hacking your account can replace or delete your messages, they can't replace or delete those messages quoting yours. But, if you are going to do it, you might as well do it correctly.