WordPress at a glance
filter is not described

admin_comment_types_dropdown filter-hook . WP 2.7.0

Filters the comment types dropdown menu.

Usage

add_filter( 'admin_comment_types_dropdown', 'filter_function_name_9624' );
function filter_function_name_9624( $comment_types ){
	// filter...

	return $comment_types;
}
$comment_types(array)
An array of comment types. Accepts 'Comments', 'Pings'.

Where the hook is called

WP_Comments_List_Table::extra_tablenav()
wp-admin/includes/class-wp-comments-list-table.php 346-349
$comment_types = apply_filters( 'admin_comment_types_dropdown', array(
	'comment' => __( 'Comments' ),
	'pings' => __( 'Pings' ),
) );

Where the hook is used (in WP core)

Does not used.