Depends on the ghost, the context, and the person. Some ghosts are harmless. Others really are not. A battleground, especially on its anniversary, is among the more mystically hazardous places. Some people are better equipped to defend themselves than others -- or to pass unnoticed, or even present as a nonthreat. The more staunchly mundane someone is, the more likely they are to pass without notice, but that's not quite a guarantee.