http://www.w3.org/TR/DOM-Level-3-Events/#dom-events-conformance sez: A DOM application may use the hasFeature(feature, version) method of the DOMImplementation interface with parameter values "Events" and "3.0" (respectively) to determine whether or not DOM Level 3 Events is supported by the implementation, and the implementation must return true.Since DOM Level 3 Events is built on top of DOM Level 2 Events [DOM Level 2 Events], an implementation that returns true for "Events" and "3.0" shall also return true for the parameters "Events" and "2.0".The same holds for the feature strings defined for the individual event modules as applicable. Refer to DOM Features in [DOM Level 3 Core] for additional information. If we support dom level 3 events, we need to return true. If we don't support dom level 3 events we should.
http://samples.msdn.microsoft.com/ietestcenter/domevents/domevents_harness.htm?url=hasFeature.Events fails for the same reason.
Welp, we don't support DOMAttrModified and we never intend to (see https://bugs.webkit.org/show_bug.cgi?id=8191) so we should not return true for this.