XML Documents should not create renderers for unrecognized tags This includes XHTML. Only regonized tags, which WebKit has support for should result in renderers being added to the Render tree and actual drawing to the screen being done. At least in the case of SVG (and other xml formats), it's common to embed additional non-rendered xml containing metadata about the document which might be used by certain (editing) programs when opening it, but should not be rendered by Safari.
According to hyatt, this is correct behavior for XML/CSS. I've special cased SVG as part of 3249's changes.
Mass moving XML DOM bugs to the "DOM" Component.