This is a bug with the forum, so I’m not exactly sure where to put it. Maybe someone can send this to discourse if that makes sense.
On mobile (at least Safari for iPhone), each top-level section (WaniKani, Japanese Language, etc.) shows the three most recent topics. However, this still includes muted topics and sub-sections, which makes it kind of annoying. I think this should be fixed to not show muted topics and sub-sections.