I recently released a plug-in for Moodle which might be relevant to this discussion on supporting the editing of equations. More details are at
http://moodle.org/mod/forum/discuss.php?d=152634, but essentially, I developed a Word template for creating questions as tables in Word, and a Moodle plug-in that converts those Word tables into Moodle Question XML, and then into the Moodle question database.
The plug-in supports embedded images in Word, and I noticed that the MathType Equation Editor for Word supports the ability to convert equations into external image files, and replace the equations with the names of the images, e.g. <<Eqn001.gif>>.
I added a macro to my Word template to insert the images instead of the placeholders, so it makes quite an effective and efficient question editor with equation support. I believe that if it was considered worthwhile, it would be possible to extend the plug-in to support the conversion of standard narrative Word content, including MathType equations, directly into HTML+images in Moodle.
This would obviously not be a HTML editor with equation support, and the equations would become images in the output HTML, but nonetheless, for those unfamiliar with any of the many formatting syntaxes for equations, or who cannot install the various filters on their Moodle servers, it might be a useful alternative.
There is a screencast demo online at www.moodle2word.net and you can also download the Moodle question import plug-in and templates from there.