Hi Jero,
You could try Eric's
QuickEdit plugin. Though this isn't actually WYSIWYG, it does provide a way of easily remembering the markup.
I've not tried EasyEdit myself though I quick test on
Pascal's homepage with Firefox 4 worked fine. I have used his FCKEditor plugin though which worked fine for me last time I used it though it does require access to the external libraries.
Have you tried EasyEdit with a clean, empty version of TW to make sure there is no other plugin messing things up? Maybe there is a problem with the latest version of TW as the plugin doesn't seem to have been updated since 2007.
Regards, Julian Knight.