Social media can be a double-edged sword for public figures. Chief Executive John Lee Ka-chiu has just had a taste of that. After making a splash on the mainland China microblogging site Weibo, those running his account caught a whiff that something might have gone wrong as complaints against the stench of a local landfill near the border with Shenzhen flooded in. The incident may have been a little embarrassing but it allowed Lee – the first Hong Kong leader to have a Weibo account – to directly feel the pulse on the other side of the border and address…