If going for subforums, I would endorse ensuring posts can be cross-posted and their comments are properly shared across the relevant subforums, or allowing such functionality as an option for the author.
Maybe you can rely on tags for this, although ensure author-added tags can only be removed by mods? I guess there’s also a question of whether you want authors to be able to easily prevent their posts from being tagged and added to other subforums they don’t want them to be in. And maybe they’ll want to keep discussions separate in some cases even if posted across multiple subforums.
If going for subforums, I would endorse ensuring posts can be cross-posted and their comments are properly shared across the relevant subforums, or allowing such functionality as an option for the author.
Maybe you can rely on tags for this, although ensure author-added tags can only be removed by mods? I guess there’s also a question of whether you want authors to be able to easily prevent their posts from being tagged and added to other subforums they don’t want them to be in. And maybe they’ll want to keep discussions separate in some cases even if posted across multiple subforums.