Based on the overall tone of essay we can infer that narrator is joking when he writes Yet at least tragedy was not without its value. Now one remembers to lock door.?

You're right to question that! The statement "Yet at least tragedy was not without its value. Now one remembers to lock the door" is highly ironic.

Here's why:

* The statement is absurd: The narrator is suggesting that the only positive outcome of a tragedy is that someone now remembers to lock their door. This is a trivial and almost insulting response to a serious event.

* The tone is sarcastic: The phrase "at least" implies a begrudging acceptance, but the actual value offered is so insignificant that it highlights the absurdity of the situation.

* The implied meaning: The narrator is likely using this statement to express a deeper feeling of disillusionment or cynicism. They are suggesting that even in the face of tragedy, people often learn little and fail to make meaningful changes.

Therefore, the narrator is definitely not joking, but rather using sarcasm to express a serious and perhaps even cynical viewpoint.