The difference is that WebKit is open source with several large companies contributing to it. If it doesn't follow the HTML spec you (or anyone else) can fix the bug.
IE was closed source and Microsoft disbanded the team that developed it (IE6). If it had a bug, there wasn't anything you could do about it. You just made your site work around the bug, possibly breaking it on other browsers.
Remember those days? This is not a good thing. The HTML spec should be the standard, not WebKit's bugs.