I have a lot of respect for Jacopo and his routes/ethics but find his reaction to this a little bizaare. Sure, he may have decided to not openly grade things based on his personal ideas about ethics and motivations or whatever, but clearly this isn't the norm in the climbing community and an appreciable understanding of difficulty is one of the cornerstones of climbing as a pursuit. It's fine for him to not put a public grade on something if he doesn't want to, but this doesn't mean nobody else can ever grade it either.
This feels more like an 'E9?! It's way harder than that, although of course I don't care about grades or grade my routes at all...'