"Acted as if he didn't know me" vs "Acted as if he hadn't known me

Question

First, here's a material that made me keep thinking about this issue in the first place.

http://www.grammaring.com/as-if-as-though

She acted as if she didn't know me.

It was the first time that I'd seen her since I was in elemantary school.(and now I'm 26). A couple of days ago, when I met her, she acted as if she didn't know me. I think she didn't remember me.

She acted as if she hadn't known me.

I broke up with her a couple of weeks ago, and when I met her yesterday, she acted as if she hadn't known me. She definitely knew who I am, but pretended as if he hadn't known me because she didn't want to talk to me.

Is it right that I make a situation like that with each sentence? I hope this try will be concerned not only for me, but also for other English learners.

Answer 1

We tend not to speak of having known someone unless there’s a fixed period of time, either explicitly mentioned or implied by the situation (e.g. the person is deceased).

With that in mind, I would switch your two usages to describe the other scenarios, with slight alteration:

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It was the first time that I’d seen her since I was in elementary school. A couple of days ago, when I saw her, she acted as if she hadn’t known me (for eight years when we were kids). I think she didn't remember me.

In this case, there’s a specific timeframe in which knowing occurred, which has since ended.

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I broke up with her a couple of weeks ago, and we saw each other yesterday. At that time, she acted as if she didn’t know me. She definitely knew who I was, but pretended as if she didn’t know me because she didn't want to talk to me.

This is the common use of the phrase. We think we either know someone or we don’t. It’s like a light switch. She acted like the light was off; she acted like she didn’t know you.

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Another common way English speakers would discuss something like this is to say “she acted like we hadn’t met” or “she acted like we’d never met”. These use “met” in the sense that you meet someone and from that point forward you know that person.

Answer 2

She acted as if she didn't know me.

She acted as if she hadn't known me.

I think you are thinking the other way round. You think she doesn't remember you or you do know whether she remembers you; it's a doubtful situation. Hence, the sentence should be in the subjunctive mood. The second sentence fits in this situation.

On the other hand, if you are talking about a real situation as you have mentioned in your second case, you should use the real tense here. You know she knows you as you broke up with her just two weeks ago. So the first sentence fits in this situation.