Surcharger la configuration par défaut de TinyMCE :

A insérer dans le functions.php

function myformatTinyMCE($in)
{
$in['remove_linebreaks']=false;
$in['gecko_spellcheck']=false;
$in['keep_styles']=true;
$in['accessibility_focus']=true;
$in['tabfocus_elements']='major-publishing-actions';
$in['media_strict']=false;
$in['paste_remove_styles']=false;
$in['paste_remove_spans']=false;
$in['paste_strip_class_attributes']='none';
$in['paste_text_use_dialog']=true;
$in['wpeditimage_disable_captions']=true;
$in['plugins']='inlinepopups,tabfocus,paste,media,fullscreen,wordpress,wpeditimage,wpgallery,wplink,wpdialogs,wpfullscreen';
$in['content_css']=get_template_directory_uri() . "/editor-style.css";
$in['wpautop']=true;
$in['apply_source_formatting']=false;
$in['theme_advanced_buttons1']='bold, italic, strikethrough, bullist, numlist, blockquote, justifyleft, justifycenter, justifyright, link, unlink, wp_more, spellchecker, fullscreen, wp_adv';
$in['theme_advanced_buttons2']='formatselect, fontselect, fontsizeselect,  underline, justifyfull, forecolor, pastetext, pasteword, removeformat, charmap, outdent, indent, undo, redo, wp_help';
$in['theme_advanced_buttons3']='';
$in['theme_advanced_buttons4']='';
return $in;
}

add_filter('tiny_mce_before_init', 'myformatTinyMCE' );