I've got a few instances of flarum setup on my own server. Both of them have some pretty long discussions, going back years, with hundreds of posts.
In the "Storyteller Forum", I've got things split between a "discussions" thread and a "game" thread (it's a roleplaying play-by-post game). My players have many times complained about not realizing which thread they're on. And since the left "thread list" doesn't always show, it's really easy to miss which thread I'm in.
Best solution? Have the title show in the top menu bar. Or pin it (maybe a smaller version) to just below the menu bar.