It appears that the NYC Comic Con guideline is "Skimpy costumes are permitted though concessions to accuracy are needed if skimpy to the point of negligible coverage i.e. less than typical swimwear."

It is, of course, up to the enforcer, but I would evaluate the Nonon cosplayer as "less than typical swimwear", and the Conan cosplayer to be about the same as typical swimwear. Some skin-colored underlayer would've made it more safe.