网友应注意：标点符号前不空格，后面要空格。你刚好弄反了，以后要注意。下面是我作了修改的，你比较一下是否清楚了很多。

There are also other more neutral views, such as those held by people who don't mind advertising, or the idea that advertising is an art form in itself, that, if viewed critically, can make a social comment on the style, artifacts of different social groups.

本句中的that从句显然是一个非限制性定语从句，补充说明先行词an art form.

在英语教学中以及一般语法书中，关系代词被认为不能引导非限制性定语从句。that引导非限制性定语从句十分少见，但并不是不可能。在实际应用中，的确有部分讲母语的人用that引导非限制性定语从句（先行词为名词），虽然很多人怀疑这种用法的可接受性。例如《剑桥英语语法》第1502页就有如下来自可靠出处的that引导的非限制性定语从句的例句：

The patas monkey, that spends almost all its time in open grassland, adopts just such tactics.

His heart, that had lifted at the sight of Joanna, had become suddenly heavy at the sight of Ramdez thumping after her.

所以，网友自己在写作中不要用that引导非限制性定语从句。但在阅读原版英文读物时，遇到that引导非限制性定语从句，不必大惊小怪，也不要认为这是错误。可以告诉自己，今天我看到了that引导的非限制性定语从句就行了。但中国人写的东西里面用that引导非限制性定语从句，则多半是由于疏忽所造成的。