答疑网确实提醒过网友，当不定式、疑问分句、that从句作主语并位于句首主语位置，如果改为问句需要倒装时，必须采用外置主语结构，用it作形式主语。例如：

To study hard is important.

Who did it is not important.

That he did it is obvious.

以上三句改为一般疑问句需要倒装时，必须采用形式主语结构，真正主语外置：

Is it important to study hard?

Is it important who did it?

Is is obvious that he did it?

你的句子中how badly引导的是间接疑问句，不需要倒装，但由于how badly必须前置引导问句，如果不采用外置结构，则how badly距离它所修饰的动词hurts太远，容易导致误解，所以为了疑问分句本身的结构平衡和避免误解，改分句还是应该采用外置主语结构。

试比较二种结构：

We can't tell you how badly it hurts that she is no longer alive. (正）

We can't tell you how badly that she is no longer alive hurts. （误）