xD Idk, some companies get very offended by it. I don't remember who, but someone shut down a fanfic site, they were so offended. But yeah, good point on the Oda thing.
Generally sites like that don't get shut down unless they're explicitly pornographic and/or using characters in a way that implies marketing. Like if you go to a site and you can watch Super Dario, a man in red overalls and shirt, having sex with Princess... I can't think of a good one that won't get me modded so let's say Princess Nice Lady.
"Murder of the living is tragic, but murder of the idea is unforgivable." - Janus, speaker of the synod
They basically made that rule to pull an Oda w/o being as hypocritical as Oda (One Piece author) I.E. claiming that One Piece would have no romance involved in it, and yet Hancock is madly in love with Luffy (confirmed) and several times in the anime it's strongly hinted at that Nami has some extent of feelings for him (fan speculation based on scenes like the Arlong fight and nearly every time luffy "dies" to enemies like Lucci and Crocodile).
Not sure about the Nami point (I personally don't see them that way), but as for Hancock, even though she's in love with him, her attraction is only ever played for laughs. Thus, the fact that she's in love is comedy, not romance.
Official Bride and Wife of Noire (of the Fire Emblem Awakening message board)