Six characters? Three? Do you have a minimum at all? Should there be a minimum length for a username? Why can’t I have a one-letter username? Obviously there’s a fair chance that someone might have taken it before me, but still, what’s stopping me? Are enforced-username lengths a security issue? If you allow one-letter usernames, then perhaps there’s a better chance of brute-forcing the password?
Regardless, it’s completely frustrating to try and sign up for an account, only to be told after you’ve entered your registration details that “Oh no, sorry, your username actually has to be at least six characters long. Didn’t we mention that? Oh, sorry.”
Well, thanks and goodbye. Your service may be great, but now I’ll never know.