[romanticyao]

sorry about that, the list is simple:

first, no space in front, end or in-between of username.

seond, username may only contain alphanumeric characters, underscores (_) and dots (.), must start with a letter(not a number) and must be a minimum length of 2 characters.

that means only those letters are allowed in username:

a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y, z

and the numbers

0,1,2,3,4,5,6,7,8,9,

and "_ " " . "