User blog comment:Dezza/Luffy in the newspaper? What's happened? (Chapter 591)/@comment-2015213-20100724120531

"But in all honesty, I think it's a valid theory that Bon Clay has somehow escaped from Impel Down and is running around pretending he's Luffy to cause confusion within the marines."

I agree, he probably survived the poison somehow,get out of IP somehow and as you said had done something big as Luffy for better or worse, all this would make sense since Luffy has been in coma for two weeks.

Also, many OP translators people says that Chopper, when reading the news about Luffy, said "what the hell?!" or something like that and not "Why again?!" This has apparently been corrected many times by now. So whatever Luffy did, it is not something he has done before.