This is the 5th or 6th time I've seen this posted, including by myself, and every time the topic has sank like a stone. I'm perplexed as to why HN doesn't consider this project worthy of discussion, given the path-breaking nature of the proposal.

Because many think HN should only be about writing the latest and greatest social app, not things that move humanity forward.

/rant

Me too. It is both exciting and disturbing. For me it also calls to mind Carl Sagan in Pale Blue Dot warning against developing the ability to move asteroids around.

Seems a little far-fetched. Talk of moving gigaton rocks - harder than for instance moving a small city to Mars?

Well, given that it's just a rock and doesn't have any people inside, it can be moved very slowly, eg by applying a tiny amount of thrust over a couple of years.