The current WYSIWYG editor in Confluence can screw up pages, that make use of more advanced WikiText formatting. I think this is because the editor makes use of the HTML editing capability of current browsers. Because WikiText has more 'capabilities' than HTML (especially with all the advanced macros), I think it cannot always be correctly converted to HTML, without loosing information.

Wouldn't it be better to stop depending upon the HTML editing capability of browsers and instead build a specialized WikiText WYSIWYG editor? Building such editor in Flash technology could be a viable option, though you could probably also build a specialized editor with JavaScript and the DOM.