If I were to make a brand new account with 0 play time, I could join Beginner, Intermediate, Semi-Pro and Blackbelt rooms no problem, until I am beyond the limits of the room.

So why is it as a non-ultimate level player, I can not join Ultimate level rooms, even though I could join the Blackbelt rooms as a white belt?

Veteran players don't want to have to deal with rage-quitters or a lack of a challenge.

That is a bit ironic, considering all the rage quitters I've met in-game were 5th-10th dan blackbelts...

I agree with him.

It is normally the wannabe pros that rage quit.

whats the qi for ultimate?

3000 Qi or 3rd Dan if you want so.
Anyways, I didn't even know you could join the Black Belt rooms without having at least 1000 Qi, because when there were no Ultimate Rooms you couldn't do so.
I think the main reason is, as Numbers said, that people want to play with people on the same level. It can be annoying to play against someone who doesn't even know how to save himself. Just let them have their few rooms.

Well you shouldn't be able to join the black belt servers. They're kinda glitchy.

Ultimate servers are for 3rd dans ( 3000 qi ) and up.
Beginner intermidate and all those other ones are from white belt to black belt ( 0 qi - 999 qi )

Black belt servers are supposed to be 1000 qi and up but they reset a lot.

Ultimate 3rd Dan to elite