Looks like Twitter fixed an old trick people used to pull to make misleading usernames. Scammers used to take advantage of the fact that lowercase L and uppercase I are indistinguishable in sans serif fonts, so you'd end up with people registering names like TWlTTER or StephenCoIbert to gin up followers for spamming and the like.

(And to reiterate another poster, that's not Banksy in any case.)