In the early days Usenet propagation was slow and haphazard because the communication links available were very limited. Nowadays I can post a message on one Usenet server and it appears on other servers in a few seconds. So coherent real-time conversations are no problem.
On the other hand, with a long-running discussion, HN, Reddit, etc. still have no way to see what messages are new since you last looked at a thread, something which Usenet clients have always done and still do now.