It was posted here too. What's cool in this case is that user X asks about the relevance of P, and user Y comes up with many months olds news on Q that happens to be the perfect missing piece in the puzzle.

This stuff happens all the time. Why is R this way? CEO of R Inc. comes up to tell you. Why is S not in space? It just so happen that a engineer from the space program is reading the comment and answers with a detailed insightful post.

When that happens, HN is awesome.