I absolutely despise Reddits layout, and I can't see how so many people can claim to spend every free hour of their life on there.
Classical discussion forums are still well suited to, well, discussion. Discussions between multiple people just don't work at all on Reddit-type layouts (IMHO, anyway).
If every thread had a simple and single answer then having one pinned to the top would be nice, but it doesn't, many questions require a lot of back and forth to determine the actual requirements and use-case, only at which point it is possible to give a precise answer.
Unfortunately its a common problem that discussions "branch" off, and the people involved would've been better advised to create a new thread, but often thats not clearly visible until its too late, and of course we can't really enforce such things either.
Threaded discussions don't solve that problem, you still have to actually find the thread you want to follow.