Current status on this in trunk:
1) All links that I tested work on Firefox 3, IE5, IE5.5, IE6, and at least one version of recentish Opera. Still needs testing on IE7, IE8 beta, WebKit, and older Firefox.
2) There are no legacy anchors in place. In other words, old links will all break. This should be reasonably easy to fix, although more than two or three lines (need to maintain and check a second array in Parser::formatHeadings() to get the numbering right).
3) Redirects to section after edit work in Firefox, but fail in IE5, 5.5, and 6, whether the HTTP response URL is urlencoded or not. With (2) fixed, these could redirect to the legacy anchor in known broken user agents. This might require some refactoring.