AuthorizedKeysFile line commented out but still seems to work

Solution 1:

That is the default location. You can use AuthorizedKeysFile to change to a different location, but if you don't specify it, then it will look in ~/.ssh/authorized_keys

From the man page (e.g., https://www.freebsd.org/cgi/man.cgi?query=sshd_config&sektion=5):

AuthorizedKeysFile

   Specifies the file that contains the public keys that can be used
   for user authentication.  The format is described in the AUTHO-
   RIZED_KEYS FILE FORMAT section of sshd(8).  AuthorizedKeysFile
   may contain tokens of the form %T which are substituted during
   connection setup.  The following tokens are defined: %% is
   replaced by a literal '%', %h is replaced by the home directory
   of the user being authenticated, and %u is replaced by the user-
   name of that user.  After expansion, AuthorizedKeysFile is taken
   to be an absolute path or one relative to the user's home direc-
   tory.  Multiple files may be listed, separated by whitespace.
   The default is ``.ssh/authorized_keys .ssh/authorized_keys2''.