Comment 2 for bug 42382

As a security feature, ssh defaults to hashing the host details when saving into the known_hosts file. This is because of possible issues like worms using the names to propagate themselves across networks.

You can disable this feature by either commenting out the 'HashKnownHosts' line in /etc/ssh/ssh_config or by putting the line
HashKnownHosts no
into ~/.ssh/config

Since bash completion should ignore hashed lines, I'll reassign this bug to bash to fix that.