Reddit-style posting is basically the same format as comment threads here, it’s just a little easier to see the threading. One thing that feels awkward using threaded comments is conversation, and people’s attempts to converse in comment threads is probably part of why comment threads balloon to the size they do. That’s one area that chat/IRC can fill in well.
Another issue is that top-level posts have a feeling of permanence to them. It’s like publishing something. I’d rather start with an idea and be able to discuss it and shape it. Top-level posts seem like they should have been able to be exposed to feedback before being judged ready to publish. I’m not really sure what kind of structure would work for this, but if I did, I probably would have jumped into an open thread or a meta thread before now :)
Hi.
edit: to add some potentially useful information, I think the biggest reason I haven’t participated is that I feel uncomfortable with the existing ways of contributing (solely, as I understand it, top-level posts and comments on those posts). I know there has been discussion on LW before on potentially adding forums, chat, or other methods of conversing. Consider me a data point in favor of opening up more channels of communication. In my case I really think having a LW IRC would help.