there’s an incompatibility with ‘PS Disable Auto Formatting’ and probably any other plugin adding filters to ‘the_editor_content’.

the problem is: calling htmlspecialchars twice. this breaks the language comments.

the solution: simply call htmlspecialchars with $double_encode = false to prevent double conversion. (http://php.net/htmlspecialchars)

i just wrote a quick fix: just add this to qtranslate_utils.php and add it instead of ‘wp_htmledit_pre’ to ‘the_editor_content’:

function qtranxf_htmledit_pre($output) {
	if ( !empty($output) )
		$output = htmlspecialchars($output, ENT_NOQUOTES, get_option( 'blog_charset' ), false ); // convert only < > &
	return apply_filters( 'htmledit_pre', $output );
}

(this is basically the same as core wp_htmledit_pre, just with double_encode off.)

add the filter with a high priority to ensure it runs after any other filter added by plugins:
add_filter('the_editor_content', 'qtranxf_htmledit_pre', 99);

https://wordpress.org/plugins/qtranslate-x/