Seeing the same news items again and again, nothing can mark them “read”. And if by some miracle one of them is marked read, then there is another stubborn one coming right after. The first 50 times it’s funny to see the same ancient article, after that you kind of want to push the DB server off a cliff, and if the article in question is poor, I sort of wish to push the author off that same cliff too.
Other than this and occasional “stuck on fetching stories” NewsBlur is a killer service. Good luck with all the upscaling.