I know my account is super new but he screen shared via skype and everything seems to be legit so far and he has done arma 3 hacks before.... *Will update*
Did a screen-sharing with him, everything seems alright. 'Gonna proceed to payment tomorow. Anyway the seller is super friendly and answer every questions !
For now I give a huge +1 to this guy who's one of the very few non scamming people out there