Thanks for answering my question — now I understand. I may be wrong, but I think it would actually work a lot better if you simply continued with the same discussion, as people who have already contributed tend to revisit discussions they’ve already commented on. You can post a follow-up question in the comments, or you can edit the original post. (Be careful when editing — if edits make some of the comments nonsensical, people won’t comment on your posts anymore, so it’s best to make it clear what has been edited.) Note that it’s easy to find discussions one has already commented on, as opposed to new discussions posted at random times of the day. Most of the thoughtful, active participants check back on the interesting discussions on a regular basis.