Thanks for this, Dave.
I’ve been running an online forum for around ~25 years, and in my full time gig, I work for a YC start-up. So, just lending my perspective for what it’s worth:
- Unless we’re using an extended Lexical (is this even possible w/ Rails?) as the composer, this feels valuable, but not vital. I think my forum qualifies at a scale you might want to observe, but new users have never complained about crafting posts.
- Registration: Great to hear, current registration is clunky from both a UX/integration standpoint.
- Notifications: I’m interested to see what you guys do here, but to me, this is intrinsically tied to my point with sidebar and tracking.
So with that segue (yes, I’m gonna pitch the team again here): the sidebar, in its current state, is a mere utility—a shortcut—to simply navigate. But that’s it. If it disappeared tomorrow, users/admins would simply carry on as they always had. In that regard, it’s another UX layer. Like an additional onramp to the same destination.
But what if the sidebar facilitated both NOTIFICATIONS and TRACKING? 
Suddenly, tracking (and by extension notifications) is no longer buried multiple layers into the preferences. It’s right in front of a user. Seamlessly adjusted as they browse.
(And in the future, AI could assist in adjusting tracking preferences for a user, like, say, an engineer who visits the same site multiple times for TypeScript topics, but can’t be bothered to adjust his/her preferences—the site would simply adjust it for them. But that’s for another day …).
Anyway, my point is the following: users are browsing more sites/apps than they ever have before. They don’t use a site like admins do. They don’t have time/patience to figure out how to manage their preferences as a site evolves. Nor should they be confused that adjusting their sidebar in zero way reflects what’s in their account preferences. WE SHOULD FLATTEN THAT EXPERIENCE FOR THEM!
OK, pitch done.
Regardless, love the team and all they do here. ~