This CSS removes the date and time from all comments across your entire site by hiding the comment meta data. It does not remove or delete the meta data associated with each comment from the database or from your source code.
This code works in child themes running on the Genesis theme framework.
This code works for the Twenty Thirteen default theme for WordPress.
Other themes may use a different class for the comment meta data which you can grab using Firebug.
You can also run a database query in phpMyAdmin to remove comments and comment meta data from specific posts using a MySQL command.