When creating a new account has no cost at all to the banned user then this is a useful response. Perhaps you have never tried to deter a determined troll or griefer on a forum, but it is a non-trivial exercise. It was not the coders admitting that they don't know how to solve the problem, it was the coders coming up with a solution that was effective for some large portion of the problem and that did not require too much additional code.
They did not screw the real user, they just made them invisible. Eventually, when their posts did not get the replies they were looking for, they might just give up and go away -- this was the intent of the system.