Here, "fingerprints" is a term of OpenPGP (the hex digits).
It doesn't mean physical fingerprints of human being.

Yes, it's a warning, but I wonder if it's good to add "警告：" here.

The context of this message is that:
(1) When a user tries to sign on User-ID (== to certify) by gpg --edit-key 's sign sub-command,
(2) GnuPG finds there is no self-signature,
(3) Then, display this message to a user,
(4) It is followed by "Are you sure you still want to sign it? (y/N)",
(5) ... which defaults to "No".

It is quite unusual with no self-signature.

Good catch. That's better.

Here, 'fork' is a technical term on Unix (creating new process).

https://zh.wikipedia.org/wiki/Fork_(%E7%B3%BB%E7%BB%9F%E8%B0%83%E7%94%A8)