不知道有什么插件。但这是可以解决的creating a custom plugin 使用Settings API 和aCustom Meta Box.

在设置页面中添加RichText编辑器/wp-admin/options-general.php

<?php
/* Plugin Name: Custom Editor in Settings Page */

add_action( \'admin_init\', \'register_settings_wpse_57647\' );

# Register settings
function register_settings_wpse_57647() 
{
    register_setting( 
        \'general\', 
        \'html_guidelines_message\',
        \'esc_html\'
    );
    add_settings_section( 
        \'site-guide\', 
        \'Publishing Guidelines\', 
        \'__return_false\', 
        \'general\' 
    );
    add_settings_field( 
        \'html_guidelines_message\', 
        \'Enter custom message\', 
        \'print_text_editor_wpse_57647\', 
        \'general\', 
        \'site-guide\' 
    );
}    

# Print settings field content
function print_text_editor_wpse_57647() 
{
    $the_guides = html_entity_decode( get_option( \'html_guidelines_message\' ) );
    echo wp_editor( 
        $the_guides, 
        \'sitepublishingguidelines\', 
        array( \'textarea_name\' => \'html_guidelines_message\' ) 
    );
}

Results in:

将元框添加到帖子/页面

add_action( \'add_meta_boxes\', \'add_custom_box_wpse_57647\' );

# Add Meta Boxes
function add_custom_box_wpse_57647() 
{
    foreach( array( \'post\', \'page\' ) as $cpt )
        add_meta_box( 
            \'mb_wpse_57647\',
            __( \'Additional Guidelines\', \'this_plugin_or_theme_textdomain\' ),
            \'inner_custom_box_wpse_57647\',
            $cpt,
            \'side\',
            \'high\'
        );
}

# Prints the box content
function inner_custom_box_wpse_57647( $post ) 
{
    global $current_user;
    get_currentuserinfo();
    $the_guides = html_entity_decode( get_option ( \'html_guidelines_message\' ) );
    echo \'<h2>Howdy, \' . $current_user->display_name . \'</h2>\';
    echo "<div>$the_guides</div><br style=\'clear:both\' />";
}