Hoi there,
I have just looked on Hearing Aid Forum - Active Hearing Loss Community (sleek) and SE23 Forum (nice).
I’m wondering if it possible to make it look like Categories - Discourse Meta or Open Knowledge Forums?
It would give much more flexibility in regard of e.g. Post Topic in Two Categories? and allows you to work with tags only.
On the downside, you have to micromanage tags and tags-group. That would require that the Tag Groups setting page need some more tools to manage them.