Como descrito em ssh-keygen man :
O usuário @ host é um comentário padrão adicionado por ssh-keygen
:
For RSA1 keys, there is also a comment field in the key file that is only for convenience to the user to help identify the key. The comment can tell what the key is for, or whatever is useful. The comment is initialized to ''user@host'' when the key is created, but can be changed using the -c option.
Você pode usar as opções -C / -c para definir um comentário diferente
-C comment Provides a new comment.
-c' Requests changing the comment in the private and public key files. This operation is only supported for RSA1 keys. The program will prompt for the file containing the private keys, for the passphrase if the key has one, and for the new comment.
por exemplo. usar o sinalizador -C ""
da seguinte maneira definirá comentário vazio na chave pública
ssh-keygen -C ""