how作为疑问副词引导名词性从句，有时疑问含义很弱，接近于that的用法。《韦氏高阶》将how 的这种用法归为连词：

: that

• She told us how she had to work hard.

• He knows how you are a valued employee.

• It's amazing how they completed the bridge so quickly.

以上三个例句中how用that替换，意义不变。

但《朗文》仍然认为这种用法的how是副词：

5 used after certain adjectives or verbs to refer to an event or situation 

It’s amazing how they’ve managed to get everything finished so quickly. 

I remember how she always used to have fresh flowers in the house.

以上二句的how也可改为that，意义基本不变。

但毕竟how是疑问副词，尽管有时how的疑问意义很弱，以致于可以用that替换，句义基本不变，但how从句仍然是wh-从句，而不是that从句。这就意味着how从句可以作介词的宾语，而that从句不能作介词宾语。

I remember how she always used to have fresh flowers in the house.

He knows how you are a valued employee.

以上二句how从句为动词宾语，因此可以改为that从句：

I remember that she always used to have fresh flowers in the house.

He knows that you are a valued employee.

我们可以让以上how从句作介词宾语：

We are talking about how she always used to have fresh flowers in the house.

We are talking about how you are a valued employee.

此时，how则不能用that替换，how也不可以省略。

网友的句子就是how的这种用法，how引导名词性从句作介词宾语。how的疑问含义很弱，接近于that的用法，但由于是介词宾语，故不能用that引导从句。