Convinced more than ever that browsers should have auto-detected RSS feeds linked from pages and revealed "subscribe" buttons if the user configures a default RSS reader. Simple protocol, good UX opportunity for everyone, and would heal a lot of URL guessing.
@slightlyoff Opera had this, there was an RSS icon in the location bar for any page with feed metadata, and clicking on it added that feed to the built-in feed reader (which was just another mode of the built-in mail client).
@wollman Yes! I have a vague memory of that. ISTM that a good answer would be even more open; I.e., if you set a different feed reader as your browser or OS default, it would send subs to that instead.

@slightlyoff @wollman You could do that back then in Safari, see the attached screenshot. And the idea for web-based feedreaders could have been navigator.registerProtocolHandler(), but afair no browser ever supported that for feed:// urls.

The modern equivalent are of course browser extensions – the latter implement the simple autodetection algorithm and send the feed url to native app with a custom uri protocol or to a web-based adress.