Prints the input fields in the form's header (subject, message icon, guest name & email, etc.)
Mod authors can use the 'integrate_post_end' hook to modify or add to these (see Post.php).
Theme authors can customize the output in a couple different ways:
1. Change specific values in the $context['posting_fields'] array.
2. Add an 'html' element to the 'label' and/or 'input' elements of the field they want to
change. This should contain the literal HTML string to be printed.