@luetage
Yes, I had envisioned that answer, but there's not a lot of room. There's not even enough room for Notes and Bookmarks. And you need to display related info: date-time, picture-photo thumbnails, titles and several preview lines, a lot of control buttons specific to rss/atom reader. And besides, what about users who don't work with desktop? - sorry, this already seems to be a "must ask" question. 🙂
Imho, both full-fledged Notes and Rss-Reader I can imagine only as a separate application with a bunch of settings and buttons, which will have the ability to synchronize with Vivaldi account.
Or... it'll be a stripped-down reader like Notes is now. Micro-reader with micro-ability.