The community is powered by Discourse, it’s quite different to the traditional “old school” forum software like phpBB and vBulletin (which powers Ubuntu Forums).
The trouble with subcategories is that there too many subjects to categorise, and we have enough already. The security subcategory request was rejected because of this (and other reasons below).
Instead, Tags have been adopted to group these together, as discussions may also be in other categories too (like #development-discussion and #tips-tricks-and-tutorials).
Subcategories for help & support currently go by architecture (exception of Hardware), since solutions can differ between platforms.
Ideally guests/members should utilise the search feature to find similar solutions first, or look at a list of topics by tag (e.g. #partitioning. We’d like topics to follow the posting guide to avoid the same questions being asked and answered over and over again.
@maro Thanks for the suggestions, we’ll add some of those. 