It's not just the language barrier or the ethics of disturbing someone's profile though. His emails read like a job application with some vague hints at an exp

It's not just the language barrier or the ethics of disturbing someone's profile though. His emails read like a job application with some vague hints at an exploit that may or may not be real. I'd say he expected a job offer or at least an interview as compensation for eventually revealing the bug. In his perception, going ahead and posting on Zuckerberg's timeline was just another step toward that goal. Breaking the rules is a somewhat glorified thing in hacker circles, and this may have contributed to his attitude. Of course, what they don't tell you when they say "break all the rules" is that only works out if you actually win in the end. And winning is an event often contingent on getting someone important to like you. For what it's worth, all of that probably wasn't done in bad faith, but it wasn't a constructive process either. It's something someone very inexperienced would do if they were desperate for a job in the USA. It's understandable behavior, and if I was on the relevant FB team I'd at least given him something to recognize his efforts. If in doubt, do the generous thing (and be it only for publicity's sake).