@Jack-Waugh I meant that the directory of categories and topics should be on one page, and then for each topic the posts in that topic should have their own page separate from the directory.
Being able to order all topics by date irrespective of category (or grouped by category) would probably be a useful feature, though it's less useful in an archive than a live forum. It would also probably be useful to be able to order by number of replies, since topics that turned out to be important tended to also generate a lot of discussion.
Being able to search/filter posts by author, title, category, or some combination of each would be useful, but sorting by them might be of limited use. For the title, I might remember what the thread was about and could think of a few words likely in the title, but not the first word. Navigating a list of posts sorted by author feels unwieldy, since chances are that the person I want is somewhere in the middle, not among the first few or last few people listed.
Another filter might be whether a user participated in a topic, i.e. including not only the author but anyone who replied. Specifying multiple users to return only topics in which all of these users participated would be a more niche but potentially still useful.
I can think of some very niche sorts as well which might be useful for finding specific discussions, but those have more to do with what I personally think might have been useful for finding past discussions that I wanted to refer back to. Those would be by number of replies by a specific user, number of replies by a specific user to a specific user (if you still have the data for what each reply was to; possibly the initial post, but which could also be another reply), or number of replies from one user to another and vice versa.
