I'm going to give my personal opinion on this.
Nigger was a derogatory word decades ago. Some may argue that it still is, and they may be correct.
But the key word here is context. And, most people on the Toribash community do not actively state their race, and (unfortunately) often times people are assumed to be white. The race that this word is used against tends to be african american, but as I said before, race is not something that most people are aware of when it comes to each player. So, that means that "nigger" can not be directed towards another player with the intent of offending them because their race is unknown.
But, racist statements can still be blatantly made, such as simply saying that "niggers aren't people" or "I hate niggers". I believe that this is the context in which the word should be banworthy.