Can i change my username here on BitcoinTalk forum? 
Yes you can change your username by paying 50 BTC
Q: I want to change my forum username. What should I do?
A: You can either donate 50 BTC to become a VIP or PM theymos asking to change your username (although he rarely accepts such requests nowadays).
A: You can either donate 50 BTC to become a VIP or PM theymos asking to change your username (although he rarely accepts such requests nowadays).