Finding a way to merge them seems like a good idea. Sometimes I come across discussion worthy news but decide not to post about it immediately to avoid duplication. I usually wait an hour or so to see if it becomes an article on NWR, but if it doesn't and if it's something I feel is worth discussing, only then will I create a thread about it.
Merging would be only way I could see of avoiding duplication while also keeping the comments on both threads.