It's actually a good marketing stunt. It shows that he likes the fan ans their work, which motivates them to produce more things that WILL get shared around, and ultimately make the game even more popular.

And since lewd is somewhat controversial, it contributes to his weird image and the fact that he doesn't give a fuck about people's opinion. It could almost be something completely artificial. That said, knowing Yoko Taro, I wouldn't be surprised if he did it without any afterthought just for the sake of it.

Jesus, there is actual porn on that Twitter link. Like, hardcore porn.

I added a NSFW warning to the link…