I am not sure exactly what changed within WordPress 2.8.4 to cause this but for a large segment of my readers there might not have been any visible updates on RSS feeds since around 6th September.

I wasn’t experiencing the problem, as email subscriptions to my own feed, and Google Reader subscriptions were not affected, because these pull directly from my feed on Feedburner which was being updated.

http://feeds.feedburner.com/Exploring-Niche-Websites

However, some RSS readers and feed aggregators actually behave themselves and subscribe to the feed exactly as it appears in my header.

http://andybeard.eu/feed

Unfortunately, those feed readers haven’t been able to access my feed, caught in some kind of broken redirection loop that I haven’t had time to fully diagnose… but it is fixed now.

I don’t know which of the plugins is really the culprit…

• If I remove a feed redirect from Feedburner Feedsmith, the original raw WordPress feed works fine… so that would make it look like it was the fault of Feedburner Feedsmith.
• However, if I switch of caching with WordPress Supercache Plus, redirects work fine as well. I currently have a slightly old SVN bleeding edge version so something may have been tweaked since. It also affects WordPress Supercache as noted my Marc at WTC a month or so ago.
• This also started happening when I upgraded to WordPress 2.8.4, so that upgrade could be blamed

If I actually looked at my Feedburner stats more often than once a month, I might have noticed before, and have to thank Internet Business Solutions expert John for nudging me about it. (he has some great email marketing info)

The Bandaid Fix

This isn’t a permanent solution, one of the plugins or WordPress 2.8.4 is doing something wrong/different, but this works.

You just need to add /feed to the list of regular expression declarations which determine which pages are not cached, by whichever variation of caching plugin you are using.

This isn’t a major issue. Anything calling /feed for your primary RSS feed should be redirected to Feedburner anyway, and the same could be true of the primary comments feed.
The only heavier load would be for comment feeds for individual posts, and feeds for things like category & tag pages.

The culprit may indeed be the Feedburner Feedsmith plugin, as comments on Marks blog post suggest that alternative Feedburner redirect plugins work without any problems.