Ah, my apologies, I looked for it but didn't find it. I note that the previous submission seems to have exact same URL, something which I thought was prevented by the submission process. A bug perhaps? Sorry, nevertheless.
As I understand, the news.arc program keeps a list of submitted URLs in memory, which go away when the program is restarted(?). In either case, old URLs can be re-submitted.
This is not always bad - some people may not have seen this the first time, and it is an interesting article. However, I always find it valuable when people point out earlier discussion, and I knew I'd seen it before, so I pointed at the earlier discussion.
For a more reliable view of what has/hasn't been posted, consider searchyc.com.
