这是搜索引擎自身的处理, 会自动忽略标点符号以及一些特殊字符, 有些是为了避免和自身的特殊操作符冲突的. 你可以看下 google 的 search operators:
Even though you can use the punctuation marks below when you search, including them doesn ’ t always improve the results. If we don't think the punctuation will give you better results, you'll see suggested results for that search without punctuation.
https://support.google.com/websearch/answer/2466433?p=adv_operators&hl=en&rd=1symbolhound 是一个专门搜索特殊字符的搜索引擎, 比如你的"[[" 这里就可以搜索出一些结果. 当然, 效果的话, 就不好说了.
http://symbolhound.com/