I looked up the two words on my Microsoft dictionary.
Reverse:
1) change something to opposite: to change something to the opposite direction, order, or position.
So this could indicate the fact that we're looking at Riku's story instead of the main protaganist, Sora; we're flipping the direction that the story's taking into another point of view.
2) go backward: to go backward, or move something in a backward direction.
This could possible play into the fact that Riku's ascending the castle going from Floor 12 to Floor 1 as opposed to Sora's ascension of 1 to 13.
3) turn something inside out: to change something so that the opposite side or part shows.
Since Riku is possessed by Ansem, who's trying to take control, this meaning could support the fact that Riku's slowly being turned inside out from the presence of Ansem's suppression.
4) revoke ruling: to overturn a previous ruling made by a lower court.
This could be Riku trying to overpower Ansem, or it could possibly be DiZ trying to escape from the judgment that Xemnas placed upon him.
5) print something white against dark background: to print text or graphics in white against a dark or colored background.
This could be a referance to the fact that Riku (being the white) is being placed into scenarios where only dark creatures dwell (the dark), such as the Heartless and the Organization.
6) turn weapon upside down: to turn a weapon upside down, especially as a sign of mourning.
This last one doesn't really fit into this, as this is what soldiers do to mourn for their fallen comrades, but it may tie into how Riku has flipped his weapon around in KHII to form a new weapon. But, I dunno about this one.
Rebirth:
1) regeneration of something destroyed: the regeneration of something that has died or has been destroyed.
This could either be the fact that Ansem is being reborn inside of Riku, or the fact that Riku is trying to rebirth himself through the expulsion of Ansem's being.
2) revival of ideas or forces: the revival of important ideas or forces, usually as part of broad and significant change.
This could be pointing towards the fact that people other than Maleficent are going to try and seize the Keyblade's power through Riku. Or it could just be reminding us that Riku's possessed. Whichever one, really.
3) reincarnation: the act or process of reincarnation.
Now, this could be the same thing as the 1st definition, hinting towards Riku and Ansem, but it could also be pointing towards DiZ's emergence, and he had just escaped from the Realm of Nothingness, thus reincarnating his presense.
So basically the title is just pointing towards the fact that Riku's possessed and he's trying to revive himself by expelling Ansem from his body. I doubt that the title has anything to do with BBS (except for maybe DiZ, but...). Although, one might say that the title is proclaiming that fact that the reversal of rebirth is occuring within the gameplay; Riku actually being devoured by the darkness and being killed by it.
