The manual encourages bad SSH practices.

The server could collect SSH public keys and use GitHub to resolve them to GitHub users to deanonymize users.

To protect yourself against this kind of problems:

1. Put this block at the end of ~/.ssh/config:

    Host *
    ForwardAgent no
    ForwardX11 no
    PermitLocalCommand no
    # Avoid keys being propose to any SSH server we connect to (ex: whoami.filippo.io)
    PubkeyAuthentication no
    IdentitiesOnly yes
    AddKeysToAgent no

2. Use a separate private SSH key for each organization you connect to. You must create a config entry to tell OpenSSH to use it. Ex:

    Host shhhbb.com
    PubkeyAuthentication yes
    IdentitiesOnly yes
    IdentityFile ~/.ssh/id@shhhbb.com

Disclaimer: I'm the author of https://github.com/dolmen/github-keygen