"Posted: Mon Nov 12, 2007." Back in 2007/2008, the userbase was small and feature requests were infrequent. Thus, a list of that sort was the logical thing to do. Now however, there are so many feature requests that many aren't even "planned" and a list just wouldn't be logical.
As for this request, if you had searched something such as "rank" "taiko" or "taiko rank" you should've seen pages of results. This shouldn't have been obscure at all.
EDIT: Okay, maybe a list wouldn't be illogical, but for many requests we really don't know whether they're planned or not (it's all up to MM/peppy). Even a list of the nice feature requests would be a bit crazy since it would basically just be a list of every thread in this forum (since duplicates are denied quickly).
EDIT 2: Dammit now I'm getting tempted to make a huge ass organized list of feature requests. I mean, I have been tempted to sort through old old requests, but this would be a big job... hmm... Maybe I could do something slowly...
EDIT 3: Okay you've triggered my semi-OCD love of lists and organization. I'll see about making one.