There is no option to change username in this forum. As mention by the reply above it is not possible to change username and the best way is to create alternative account.
Anyway, why want to change username? Do you feel your privacy gets compromised? Many of the users here are doing KYC including myself especially those days of bouny hunting in ICO projects. So, I think you can get used to it.
I want to change my name because a lot of people follow my old name and I don't like that.
Do you understand?
By default SMF forum member can change their name but if the community is growing the admin should change it because the name and reputation go together when you are part of the forum, this is one bad excuse and a lame one if you asked me, but you can try your luck creating another account is your best option this account is only Junior member you only need one merit and more activity to reach it on your another account.