I've seen those in the past for RSS feeds from Substack - https://simonw.substack.com/feed https://simonw.substack.com/feed for example - which is frustrating b

I've seen those in the past for RSS feeds from Substack - https://simonw.substack.com/feed https://simonw.substack.com/feed for example - which is frustrating because the whole point of an RSS feed is to support polling by automated systems!