Escaping of special characters like < >

If a user edits a text and inserts some html/xml fragments into his text and escapes them with < > everything is working fine for the moment. But if the user switches from WYSIWYG to WIKI-Editor the entities are resolved to < >. Switching back to WYSIWYG gives a warning that the XML will not be displayed anymore. Again switching back to WIKI shows that the xml-fragment is lost.

I would like to see those entities stay in place or is there another way to escape inserted tags?