Does the top comment in _every_ HN post have to be an argument, criticism, or complaint? If you don't find value in a given post, then just move on. I suspect a lot of folks had indeed never heard of this feature before now.

I found this introduction to git add -p to be extremely helpful. I've found myself in the position he describes (wanting to logically separate changes I've made to a file) many times, and I've usually handled it in a sub-optimal manner (making one commit that describes multiple changes).