Modify the Leave a Reply title above comment form
<?php
//* Do NOT include the opening php tag shown above. Copy the code shown below.
//* Modify the Leave a Reply title above comment form
add_filter( 'comment_form_defaults', 'sk_comment_form_defaults' );
function sk_comment_form_defaults( $defaults ) {
$defaults['title_reply'] = __( 'Leave a Comment' );
return $defaults;
}