I’m testing a new version of the FeedWordPress Duplicate Post Filter. It uses a new strategy for detecting duplicates which I hope will be better than previous attempts. If you’d like to test it, you can get it here. Install it by clicking the right-clicking the link, choosing “Save As…” (or whatever your browser supports for link downloading), save it to your local disk and put it in your
plugins directory. Then activate it. Let me know how it goes. If I hear some positive feedback, I’ll release it in a week or two.
Important: You need to have FeedWordPress active before the duplicate filter. This is because the filter hooks some functions in FeedWordPress and if it isn’t active, this filter can’t properly install itself.