Who said anyone needed to get banned over rumors? Besides, the topic is pretty much a discussion for Batman 3 in general.
In my eyes, Eddie Murphy couldn't pull off The Riddler and it's not even because he's black. It's because I don't think he has what it takes to be The Riddler. I don't think I have ever heard of a single non-comedy non-children's film that Eddie Murphy has played in. I agree that Depp would be perfect.
Also, for more Riddler speculation, here's a clip from Wikipedia:
The Riddler's criminal modus operandi is so deeply ingrained into his personality that he is virtually powerless to stop himself from acting it out (as shown in his third comic book appearance). He cannot simply kill his opponents when he has the upper hand; he has to put them in a deathtrap to see if he can devise a life and death intellectual challenge that the hero cannot solve and escape. However, unlike many of Batman's themed enemies, Riddler's compulsion is quite flexible, allowing him to commit any crime as long as he can describe it in a riddle or puzzle.
After a teacher announces that a contest will be held over who can solve a puzzle the fastest, a young Edward Nygma sets his sights on winning this, craving the glory and satisfaction that will come with the victory. He sneaks into the school one night, takes the puzzle out of the teacher's desk, and practices it until he is able to solve it in under a minute. As predicted, he wins the contest and is given a book about riddles as a prize. His cheating rewarded, Edward embraced the mastery of puzzles of all kinds, eventually becoming a carnival employee who excelled at cheating his customers out of their money with his bizarre puzzles and mindgames. He soon finds himself longing for greater challenges and thrills, and dons the guise of the Riddler to challenge Batman, who he believes could possibly be a worthy adversary for him.
Some writers have suggested that the Riddler's compulsion stems from parental abuse that he endured as a child. After Edward got high scores on some important tests in school, his father, unable to grasp the fact that his son was brilliant, beat him out of envy. This, in theory, left him with a strong internal desire to tell the truth, and prove his innocence. This desire manifests itself in the form of his obsession with riddles. Other writers have suggested that his madness, as well as his descent into crime in general, have roots in a yearning to rise above the anonymity that he possessed as a youth.
Such a background and personality would, I think, be absolutely perfect for the third movie and I hope that he is at least portrayed as such even the slightest.