The XenForo feed reader works just fine. But I think it needs some tweaks. It definitely is not user friendly at start up and it causes issues for a imported forum that already has most of a feeds articles posted.
It looks like it is auto set to a 5 article limit. This needs to be user defined. Especially on a new feed entry.
I have found that best practice, when adding a feed into a feed poster, is the ability to test run a feed and mark any articles you choose as pre-cached. Then you start off with only the articles you want, or in my case on a newly imported forum, skip all the articles I already have. I wasn't able to do this and I had to soft delete a mess of threads in hopes that it will keep the re-posting at bay until they fall off the feed.Plus I had to run them over and over because of the 5 article limit. Manual pre-caching is a good thing.
After many years of coding and maintaining Articlebot for vBulletin I found it's really best to cache the article title and compare it to the feed and never to the thread. Then have the cache set to prune after a set number is reached. Usually a number a little higher than the number of articles in the feed just to be sure. This way, the only way you get a duplicate is in the rare instance that the feed source changes the title.
Not a big deal but the pain could easily be a avoided with a few small tweaks.
Thank you for your time and effort in making this fine product.