Suggest HN: Permit user to collapse all earlier sibling comments
A | -- B, a response to A | | | -- the first response to B | | | -- ... | | | -- the ninth response to B | -- C, a response to A
By the time I get to C I don't know what it's talking about, because I've forgotten what A was. It's possible to collapse the thread under B, but it's a slow process hard -- I have to scroll back up, eyeballing the indentation to see when it reaches the same level as A2. And that's assuming there's only one comment thread (B) between C and it's parent; if there are multiple, I'd have to collapse them all.
Even better would be a "show ancestors" button, to collapse not only siblings above, but also the parent's siblings above, and the grandparent's siblings above, etc leading all the way back to the OP. (I would have made that the title of this suggestion, but I didn't know how to convey the idea briefly enough.)