Admin moderates ALL comments (including post author)

Try this: Capability Manager http://wordpress.org/extend/plugins/capsman/ and also read (if you have’t already done so) the WordPress roles and capabilities docs: http://codex.wordpress.org/Roles_and_Capabilities

404 Not Found

Not Found

The requested URL was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.