你所说的这本书的解释是很勉强的。它并没有解释为什么前半部分相当于Unlike what people generally supposed。

多数词典给只给出了unlike的形容词词性，而形容词unlike是不可能修饰generally supposed这个过去分词短语的。反过来，generally supposed这个过去分词短语也不可能修饰形容词unlike。 所以唯一能合理解释的只有unlikely为副词，修饰过去分词短语generally supposed。所以我们需要做的唯一一件事就是查找unlikely是否可以为副词。而the freedictionary恰好给出了unlike可以是副词的解释。

un•like•ly

 (ʌnˈlaɪk li)

adj. , -li•er, -li•est,

adv. adj.

1. not likely to be or occur; improbable; doubtful.

2. holding little prospect of success; unpromising.

Adv.

3. in an unlikely way.

网友的这个句子中，unlikely为副词，修饰generally supposed。generally supposed意为被人们普遍认为的，unlikely generally supposed则意为不可能被人们普遍认为的。这个过去分词短语作评注性状语，表示说话人对句子的评论。句子可以做如下改写：

Unlikely generally supposed, good example has enormous impact on others. 原句为过去分词短语作评注性状语

Unlike what people generally supposed, good example has enormous impact on others. 介词短语作评注性状语

It is unlikely generally supposed that good example has enormous impact on others. 外置主语从句

Good example has enormous impact on others, which is unlike generally supposed. 非限制性关系分句