The article probably struck a chord with people who either feel the same way as the author of the letter, or can strongly empathize with her feelings.

Two things, I'd guess

1) This feeling of longing, helplessness, and futility resonates with a lot more people than you might expect from sitting on a park bench watching passersby

2) Lots of HN people have hot takes, of varying quality, on how one should behave in light of such a situation.

The resulting discussion here makes this post worth it. Such a fascinating and insightful thread!