A rudimentary shim for textContent support in IE 8. It works by wrapping the items that can create HTML elements, and adding the getter on there directly. The check at the end then applies it to any existing HTML. That means you need to include this, after the HTML on your page.

gistfile1.js

    var div = document.createElement('div');
    if ( 
            div.textContent === undefined &&
            div.innerText !== undefined
    ) {
        // handles innerHTML
        var onPropertyChange = function (e) {
            if (event.propertyName === 'innerHTML') {
                var div = (event.currentTarget) ? event.currentTarget : event.srcElement;
                var children = div.childNodes;

                for ( var i = 0; i < children.length; i++ ) {
                    addProps( children[i] );
                }
            }
        }; 

        var textDesc = {
                get: function() {
                    return this.innerText;
                },

                set: function( text ) {
                    this.innerText = text;
                    return text;
                }
        };

        var addProps = function( dom ) {
            // these only work on non-text nodes
            if ( dom.nodeType !== 3 ) {
                Object.defineProperty( dom, 'textContent', textDesc );
                Object.defineProperty( dom, 'insertAdjacentHTML', insertAdjacentHTMLDesc );

                // just in case it's been attached once already
                dom.detachEvent("onpropertychange", onPropertyChange);
                dom.attachEvent("onpropertychange", onPropertyChange);
            }

            return dom;
        }

        /*
         * Wrap insertAdjacentHTML.
         */
        var insertAdjacentHTMLDesc = function(pos, html) {
            div.innerHTML = html;
            var children = div.children;

            var p = this.parentNode;
            var first = undefined;

            if ( pos === "afterend" ) {
                first = children[0];
            } else if ( pos === "afterbegin" ) {
                first = this.firstChild;
            } else if (
                    pos !== 'beforebegin' ||
                    pos !== 'beforeend'
            ) {
                logError("invalid position given " + pos);
            }

            while ( children.length > 0 ) {
                var child = addProps( children[0] );

                if ( pos === "beforebegin" || pos === 'afterend' ) {
                    p.insertBefore( child, this );
                } else if ( pos === "afterbegin" ) {
                    this.insertBefore( child, first );
                } else if ( pos === 'beforeend' ) {
                    this.appendChild( child );
                }
            }

            if ( pos === 'afterend' ) {
                p.removeChild( this );
                p.insertBefore( this, first );
            }
        };

        // wrap createElement
        var oldCreate = document.createElement;
        document.createElement = function( name ) {
            return addProps( oldCreate(name) );
        }

        // add properties to any existing elements 
        var doms = document.querySelectorAll('*');
        for ( var i = 0; i < doms.length; i++ ) {
            addProps( doms[i] );
        }
    }