I forgot to mention that I think your case makes more sense for actual users than SEO. In a large regional forum I imagine there’d be a lot of topics that both
- Don’t specifically mention the region in the title
- Are generic enough to be relevant for many regions
So a URL in isolation like community.example.com/t/springfield-restaurant-recommendations could really apply to tons of regions in the US… though sharing a link without context is pretty rare… more likely someone would say:
Check out these restaurant recommendations for your trip [to California]:
community.example.com/t/springfield-restaurant-recommendations