[k1m]

Thanks! I haven't given the issue of unique identifiers too much thought because in most cases I assume the item URL is less likely to change than the text and will serve as the unique identifier for the RSS reader. It's possible to create feeds without item URLs in Feed Creator, so in those cases maybe letting users select an identifier to be the guid element in the feed would be helpful.

Generally though, I'm hoping users understand that feeds produced in this way could be a little more brittle than if the site offered its own feed.

One difference with your approach is that you have the data from previous fetches in your database. With Feed Creator everything related to producing the feed (source URL, selectors, filters, etc.) is embedded in the feed URL to avoid having to record data on the server. So each request is treated as if it's the first one - the server doesn't know if an item in the feed is new or old. If we referred to feed data from previous fetches, maybe we could let users introduce a delay before having a new item added to the feed. This might help in cases where a typo is spotted and corrected by the publisher minutes after publication. Can't think of a much better way of avoiding false positives at the moment though.