I have seen a couple of good discussions on Lobste.rs The number of users is not very big- they're invite only. I know that some HN regulars are posting there

I have seen a couple of good discussions on Lobste.rs The number of users is not very big- they're invite only. I know that some HN regulars are posting there so maybe you could ask for invite here or head over to their IRC and then try it out. I don't use it myself, HN is big enough time sink as it is.