Even more so when it's a major topic with hundreds of upvotes and comments. Often the top comment of big big big stories on HN tends to be responsible for around 25% of total thread comments, if not more.

Niche stories with less attention tend to have a more rounded discussion with a larger number of parent comments relative to replies.

Can some kind of summary/NLP analysis help to avoid this? Some kind of color coding of the comment threads. Like which comment threads are sticking to single topic. Which are changing/adding new topics to discussion. A visual tool that can help navigate the jungle of different discussions.

How do you beat the "tyranny of the reply"?

Automatic karma deductions for 3rd tier replies? Detachment + quoting after the 2nd tier? Positioning based on the cumulative karma of the whole tree? Automatic collapse of higher tiers (a la reddit...) Super-powered collapse buttons, for when people get tired mid-tree

I wish something were done, but I bet it will be an addon, not HN, first.

Take the natural logarithm of the comment karma, and then use as the weight in a weighted shuffle algorithm?

Higher-voted comments will then be more likely to move up, but not guaranteed.

(You might want to consider putting a thumb on the scale to distinguish between comments which are low voted because they're uninteresting, and comments which contain flame-bait words etc.)

Maybe some per-user jitter in the ordering so that different people are seeing very slightly different things at the upper end, giving those posts the chance to be seen?

I like the comment collapse idea but i think it would be worth having a sorter so you can see the top comment thread but also newest first and most up-and-coming threads.