You can sign a message from one address and use another address for your storage and transactions.

A wallet for signing a message can be an empty wallet and you don't lose anything by signing a message.

People stake their Bitcoin address and message because they need other forum members to quote that message, and verify it. The most important is quoting it because if no member quote it, if a Bitcointalk account is compromised, hacker can delete that post.

You even don't need to sign a message initially, post a public address is enough. If you want to prove your ownership on it in future, you can sign a message with its private key.