If you're Chrome user by any chance, you can try also my simple extension:

NavigComments @ Hacker News

https://chrome.google.com/webstore/detail/aelihpmbbbpmljkdco...

Supports hiding comments marked as read.

Works only with http://, I have to add https:// one day, but I always forget it... Also some other things should be improved, then I could update NavigComments @ LWN too.