The protocol 2 parts of the ssh manpage says: The server checks whether the matching public key is listed in $HOME/.ssh/authorized_keys and grants access if both the key is found and the signature is correct. This is not correct. It checks for authorized_keys2.
I just checked the behavior of openssh*3.4p1-1 from Limbo2, and for protocol 2 (I didn't try protocol 1) it actually looks at both authorized_keys and authorized_keys2.
NOTABUG - authorized_keys2 is deprecated and has not been mentioned since v2.9.9p1. It is still checked for backwards compatibility
Hmmm... this bug is still open, and in "NEW" limbo...