Currently watching categories is opt-out. On forums having lots of new topics, this results in a huge number of items in example.com/unread. I think the unread page would be far more useful if watching categories was opt-in. That way /unread would contain only the items a user is interested in from the start and they won't have to go ignore a bunch of categories in order for /unread to become useful.
Hashtag feature or plugin
Stumbled on this unique variation a little earlier and thought it even kind've loaded like something you'd see on NodeBB.
Wasn't sure what the devs here had thought about some sort've #hashtag functionality, but here's one idea.
That's neat! It could definitely be done in the form of an extensible plugin.
We made the decision early on to not include hashtags into the core functionality, as we felt that we wanted to focus more on the original forum experience.
But this is perfect as an add-on.