JS Errors / White font / No TinyMCE

I am wondering why this annoying error which is documented since more than two years is still not completely fixed.

The error happens because the script loader adds a backslash to every double quote to parse the javascript code inside php code.

if i add

?>

<script type=”text/javascript” src=”https://www.mysite.de/wp-includes/js/jquery/jquery.js”></script&gt;
<script type=”text/javascript” src=”https://www.mysite.de/wp-admin/js/editor.js”></script&gt;
<script type=”text/javascript” src=”https://www.mysite.de/wp-admin/js/utils.js”></script&gt;
<script type=”text/javascript” src=”https://www.mysite.de/wp-includes/js/quicktags.js”></script&gt;
<script type=”text/javascript” src=”https://www.mysite.de/wp-admin/js/nav-menu.js”></script&gt;

<?

to the admin-header.php most of the errors will go. The font will be black again. But tinymce still does not work.