Their personal life was regularly discussed by people who did not know them but talked as if they were close friends.

这是人教新课标高中英语课本上的句子，as if they were close friends 是陈述语气，不是虚拟语气。若是虚拟语气，则是：as if they had been close friends。 

Their personal life was regularly discussed by people who did not know them but talked as if they were close friends

参考译文：他们的个人生活经常被那些不认识他们，但却像亲密朋友一样交谈的人讨论.

talked as if they were close friends如果是真实的，就是陈述语气，如果不是真实的就是虚拟语气。

提问者应该先搞清楚这样两个句子的含义，而不是看句子外表形式

1. They talk as if they are friends.

2. They talk as if they were friends.

它们表达是含义是什么？

这样的句子涉及三方

作者，// they, friend(s)   [即they里面有AB两方]

第一句作者不清楚they是否是朋友

第二句作者清楚they不是朋友

(这是对as if they are/were的主流认识，但也会有地域的差别)

He acts as if he were a student.

----> 这个He你清楚，比如他其实是你小区的保安，今天居然穿戴得像个学生。

所以提问者应该站在作者的立场，依据上下文，看看they是不是朋友这个前提

提问者给出的句子，人称太多，没有上下文，也没必要去猜谁是谁。

另外，

上面的句子2，如果往前推一格

可以是

3. They talked as if they had been friends.

也可以是

4. They talked as if they were friends.

但3有可能会改变了原句的含义。

类似的

If I were you, I would do sth

If I were you, I would have done sth.

这两句都用的是were.

结论是

虚拟语气与过去式，的确是有外形相同的时候的。

再如They talk as if they knew sth.

刘老师的例句：

1.And he sprang up, drawing his knife as if he had been twenty.  

2.Sometimes a shuddering terror struck him, as if he had been the author of the doom. 

来自英语文学作品，有权威性。但是这些作品都是100多年前的，在当时这些用法是正确的，但在现在已为视为错误。现代英语中，as if表达一个过去虚拟状态时，不再用as if...had been，而直接用as if...were

如

He walked as if he had been lame.

上面这句话已被视为错误。来看母语者的回复：

This sentence is grammatically not correct. Here ‘had been’ is wrongly used instead of ‘were’, because the meaning of this sentence is in Subjunctive mood. Therefore you should set the sentence in the following way.

“He walked as if he were lame.” (but he was not lame)

但是如果不是用be表达状态的话，had依然是成立的

The house was in such a mess – it looked as though a bomb had dropped on it.