Because it interfered with the traditional way of hiding scripts from noncompatible browsers.
因为这与从非兼容浏览器中隐藏脚本的传统方式是相冲突的。
2
In fact, in Firefox 1.5, E4X was disabled by default on HTML pages because it interfered with the traditional way of hiding scripts from noncompatible browsers.
事实上，在最新的 Deer Park alpha 版中，对 HTML 网页默认禁用了 E4X，因为与从非兼容浏览器中隐藏脚本的传统方式有冲突。