Anyone can put 'Zanpakuto:(name here)' in their bio, similar to in SL when people tried to put that they had CS2 and SSTE.
From what I've seen, nobody has any way to indicate that they have a Shikai other than to say 'I have Shikai'. Going on what the MotD said, I had though our weapon name would change to fit what we picked as our sword's name....I must have misread it, along with everyone else. =\