If the reply gets beyond a certain depth there is a built in delay (that gets longer the deeper you get). It's there because Hacker news has decided that there

If the reply gets beyond a certain depth there is a built in delay (that gets longer the deeper you get). It's there because Hacker news has decided that there is no value in deep conversations, they prefer the more shallow ones and feel that they get a better result that way. Presumably it also serves as a brake on certain kinds of anti-social behaviour such as flamewars and trolling. It's in the terms of service or rules for newbies or something like that. (edit: went looking for the text in the guidelines so I could link it, but couldn't find it. Sorry. It might be one of PGs articles that I was thinking of)