Moodle is an online application that may allow you "viewing" Word docs throug the embedded document viewer. This is a browser plugin that know how to "display" the document, but who does not know how to change it. Major reasons of this is dued to computer security issues. Changing a document (specially in Word) assume recording some big amount of data upon your local filesystem, temporary copy of the document, and using your local version of Word. All this is really "unacceptable" in terms of system security. Too many risks of intrusions and malicious macros.