“I guess they don’t want anyone to be able to do it, because someone could copy another’s screen name. “
DY: I emailed them that problem a while ago, but didn’t get a response. They should make nickname unique.
OneOfMany: Others have had problems with that link – it looks like it works for some accounts but not for others. If it doesn’t work, then I guess your only hope is to get a mod to do it.
Alternatively, donate to Kupat HaIr and try again.