Bearminator has said on a different post about this that there's also a rule that users of PokeMMO will obey rules set by the staff. He said that the staff tell you on global to not mention drugs, therefore people shouldn't talk about drugs.
Again, that's a paraphrase of what Bear said. Personally, I think most things should be allowed - obviously nothing 18+ but like jokes about drugs or alcohol should be fine. I've seen people make pedo jokes and apparently that's ok.