Who exactly knew who Moridin was? A lot of shadowspawn and darkfriends knew but they are either all dead or on the run. They are not going to be stopping to tell anyone. Aside from that the only others who know are Nynaeve & Moiraine and Nynaeve already suspected something was up and we don't really know what Moiraine knew but she has shown she never ever gives out information unless she has to.

I could see some in the inner circle of the light knowing but with Elayne as Commander in Chief with Aviendha backing her up Moridin could be marked as just another injured man, given the scale of the battle there were plenty of those around.