For HN specifically, collapsible comments would make a huge difference. A top-level comment in position one can have dozens of comments under it, making the next comment (which is perhaps only 1 upvote lower) appear far, far down the page.
If you could collapse the top level comments, this problem would evaporate.
This is exactly why HN needs collapsible comments. Not so I can collapse them for my convenience, so that stuff doesn't get buried so easily. Sometimes the top thread is all there is on the first page ... for example, there was this great blog post by raganwald a while. Here's the new version [1] since I assume the posterous one won't be around much longer. And here's the HN discussion of the original [2] in which, as he noted, a comment about IQ testing (completely tangential to the post) took the whole first page.
In that case, you would collapse the top comment chain and be shown nothing underneath, since HN only shows X amount of total comments before requiring you to click More.
I think HN would have to increase the total number of comments per page before allowing collapsable chains.
That's true, once it got that big, but I think the hope is that it wouldn't necessarily remain the top comment under those circumstances. Allowing people to collapse the thread, before it took a whole page, would allow them to see and upvote the other comments if they wished.
If you could collapse the top level comments, this problem would evaporate.