It used to be visible in the URL bar until browsers killed that feature.

Agreed! For Firefox, those features can be put back there with 'Awesome RSS' and 'RSSPreview':

https://github.com/shgysk8zer0/awesome-rss

https://github.com/aureliendavid/rsspreview

no, the paragraph argues that something needs to be glued together, which is not true, so it is not entirely about 'visibility'.