Index: src/wp-includes/class-wp-editor.php
===================================================================
--- src/wp-includes/class-wp-editor.php	(revision 38298)
+++ src/wp-includes/class-wp-editor.php	(working copy)
@@ -1259,6 +1259,14 @@
 			var init, id, $wrap;
 
 			if ( typeof tinymce !== 'undefined' ) {
+				// Fix RTL
+				tinymce.on( 'addeditor', function( event ) {
+					event.editor.rtl = event.editor.settings.rtl_ui ||
+						( event.editor.editorManager &&
+						event.editor.editorManager.i18n &&
+						event.editor.editorManager.i18n.rtl );
+				}, true );
+
 				for ( id in tinyMCEPreInit.mceInit ) {
 					init = tinyMCEPreInit.mceInit[id];
 					$wrap = tinymce.$( '#wp-' + id + '-wrap' );
Index: src/wp-includes/css/editor.css
===================================================================
--- src/wp-includes/css/editor.css	(revision 38298)
+++ src/wp-includes/css/editor.css	(working copy)
@@ -392,6 +392,11 @@
 	cursor: pointer;
 }
 
+.mce-btn .mce-txt {
+	direction: inherit;
+	text-align: inherit;
+}
+
 .mce-toolbar .mce-btn-group .mce-btn,
 .qt-dfw {
 	border: 1px solid transparent;