剑桥英语语法也谈到了这个问题（p 1112) .

(f) Verbless clauses: reduction to a single element

The extreme case of reduction is where only a single element remains:

[20] i We spend more time in France than [ in Germany].[PP]

ii He seems to play better drunk than [ sober].[AdjP]

iii More believed that it was genuine than [ that it was a hoax].[content clause]

iv It is better to try and fail than [ not to try at all].[infifinitival clause]

v Sue phoned Angela more often than [( ) Liz ( )].[NP]

vi He has more enemies than [ friends].[nominal]

In all of these it would be possible to add material in the position of the gap: for [i] wecould have We spend more time in France than [we spendin Germany],

and so on.

Reduction to an AdjP, as in [ii], is restricted to cases where the AdjP is adjunct: we cannot omit the it is in [4i] (The swimming-pool is as deep as it is wide) where the AdjP is predicative complement.

当比较分句省略到只剩一个形容词时，这个形容词只限于作状语。如果形容词为表语，例如下面句子中的 it is 是不可以省略的。The swimming-pool is as deep as it is wide.

这和章振邦的说法是一致的。所以，The girl was as brilliant as she was beautiful.这个句子中的she was是不可以省略的。

看了网友引用章振邦教授的叙述，仍然不太明白所要表达的意思。我觉得，不必背诵这些条条框框，否则会把自己弄糊涂的。把这三个句子搞清楚就行了。

1. The girl was as brilliant as she was beautiful. （这句话的 she 不可能指另外一人）

=The girl was as brilliant as beautiful.（同一个人既聪明又漂亮）

2. The girl was as brilliant as her sister was beautiful.（主句的主语聪明，从句的主语漂亮。两人各自的特征，在程度上是一样的）