Yes, it's my Jumble fork. It was born for exploring the #groupednotes paradigm, I'm trying to optimize some related UX, and probably I will explore more ideas about content discovery. The bookmarking is not visible in Jumble because no user is logged in. Btw, with the two images, I was pointing out how much cleaner and distraction-free the interface can be browsing by author and disabling web previews.

Curiosity: which client are you using? Damus?