Hacker News Reader

It's useful for the new users too because previous discussions has a lot of comments to read.

By the way, it would be great if there would be a "Related" widget with the number of comments somewhere in the comment page.

Clicking on the domain name is close to that.

As they say, close but no cigar. I come to the comments and find previous discussion because of a helpful user. Not because I knew to look for it.