hmm, I never use the wysiwyg editor, so that might be a bug.
as for the output, what you see it not what the browser actually received. For example firefox\mozilla displays the evaluated html when you view the selected source. Use the "view page source" to see the actual code.
With HTML entities the actual HTML code is
HTML Code:
<a href="mailto:%74%65%73%74%40%65%6d%61%69%6c%2e%63%6f%6d">test@email.com</a>
and with Javascript it;s
HTML Code:
<script type="text/javascript">document.write(unescape('%3c%61%20%68%72%65%66%3d%27%6d%61%69%6c%74%6f%3a%74%65%73%74%40%65%6d%61%69%6c%2e%63%6f%6d%27%3e%74%65%73%74%40%65%6d%61%69%6c%2e%63%6f%6d%3c%2f%61%3e'));</script>