Thanks for your response.
It's the categories that are the problem, not the various ways you group the questions (i.e. activity vs home page). I don't see much problem with those pages, per se. The real issue is that for each category, you have three different URL's for the same exact category. That really doesn't make sense. From a user perspective, I want to click on a category and then maybe sort that category by most popular questions, most answered etc. There shouldn't be three URL's for each category page. It is simply not useful and repetitive. Clearly, there needs to be a canonical URL for one of the categories. Which most can add manually. But, that doesn't help the usability issue or the maintenance issue (i.e. if you want to customize a category page, you end up having to customize it in three different places really).
As for Wordpress, there is always only one URL associated with each category, even if you can display content in various ways. You don't have 3 different URL's for each specific category. I've actually never seen anything like this. I really think it should be fixed (though of course, I plan to fix it manually with some coding) and that each category has one category page, which displays the questions in that category. The category page should allow for pagination, and sorting of the questions in that category by popularity, recency etc. That would make the category pages very useful