It's not about a lack of English language skills. His English is actually good enough. In the post he posted on Mark's wall you can see the language is good en

It's not about a lack of English language skills. His English is actually good enough. In the post he posted on Mark's wall you can see the language is good enough and I saw the video interview too where he even spoke well enough. A technical and step-by-step report was well within his capability. He could attach screenshots or create a video demonstration. He used the bug on real users (2 of them!) one of them being Mark Zuckerberg which has obviously created huge negative PR for Facebook. If someone tests a bug on your Facebook account how happy would you be? Facebook can't reward someone who used a bug against its users. On top of that he has damaged their reputation too. Almost all major news sites have written headlines similar to "Palestinian developer hacked Mark Zuckerberg", "Security vulnerability found in Facebook" etc etc which I'm sure they are not super thrilled about.