I'd assume you yourself could shed some light on this. I'd have to guess you're someone who saw my Twitter post and came on here to give more backlash (AE affiliated, most likely). But assuming you're not, they found mine because of a mistake I made myself. The Skype I used for trades and such was linked to a Facebook account, which had my username for AQW in its username.
Do not EVER trust new users, users with a low post count, or anyone who EVER even hints at wanting to know your username.