I've provided some custom CSS for this before:
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.