SetMoodlePlainTextEditMode.user.js

// ==UserScript==
// @name        Set the editor mode
// @namespace   
// @description Set the Plain Text Mode within Moddle
// @include     http://courses.cs.westga.edu/*
// @version     0.1
// @grant       none
// ==/UserScript==
//
//  This script will change the default Plain Text editor format
//  to a specified option rather than "HTML format".
//
//  The current setting in this script is for Markdown format.
//
//  1: HTML format
//  2: Moodle auto-format
//  3: Plain text format
//  4: Markdown format
//
//  Written 20150105

var desiredTextFormat = "4";

function setSelectedIndex(selectionBoxId, value) {
    selectionBox = document.getElementById(selectionBoxId);
    if (selectionBox != null) {
        for (var i = 0; i < selectionBox.options.length; i++ ) {
            if (selectionBox.options[i].value == value) {
                selectionBox.options[i].selected = true;
                return;
            }
        }
    }
}

window.addEventListener("load", function(e) {
    setSelectedIndex("menusummary_editorformat", desiredTextFormat);
    setSelectedIndex("menuintroeditorformat", desiredTextFormat);
    setSelectedIndex("menupageformat", desiredTextFormat);
}, false);