What happens when you have perfectly fine, years-old code that works without a hitch, passes validation and whatnot?
Well, something else breaks, of course. Feedly, in particular, seemed to be having trouble with individual RSS item timestamps, so items were duplicated every few hours. I still have no idea why.
I’d like to blame standards, but I suppose there was something else fundamentally wrong so I switched the feed format to Atom and updated a few things accordingly – there should be one more massive refresh, and things should settle from there onwards.
If that’s not the case I suggest you try re-subscribing to the feed, and apologize for the inconvenience.