Searching how ? In a search engine ? I guess the described trick above wouldn’t show there (the subdomain, I mean). The search engine will use the domain.xxx/c/category/ URL. But do people really care about the URL before clicking on a link in a search engine ? They also see the page title and the summary of the page. On top of that, google seems to show “forum-base-URL › category › subcategory” as the “URL”, so the category appears pretty clearly for what you want/your thinking.