Another reason why categories are stupid / won't work: there's no way of categorising posts after they've been made, so if a topic goes off in a different direction (as is Talkback's way) you can't add a subsequent category tag to identify it as such. At least general users can't, which means that it will have to be done by moderators and admins, and I'm pretty sure that moderators aren't going to bother, so basically you will have to.
This is therefore a filing system that exists purely for you to operate, from deployment to benefit. Which is fine, if that's what you want.
This is the perfect example of why categories are useful. Some people or functions, perhaps not you, may want a topic to be identifiable. But our philosophy is one constant stream of posts - the default threaded view.
I'm going to give you special dispensation to not be compelled to argue about stupid stuff. You can tell the "category police" police to fuck off, with my permission. Plus, luckily, categories are of no use or interest to you, so you wont care where they put it. Because, remember, the threaded view will continue to work exactly the same.
You have a different idea of 'not work' to me.
Filling something as a starting topic, and then wandering off subject is fine. It will still provide more of a sort guide than nothing at all. Search will continue to be useful, and is much improved here.
It's just a rough sort to helpfully categorise posts. It's not the stasi.