Paedophilia is a disorder where you're attracted to people who are not physically mature. So if you're attracted who is younger than they look, it's not paedophilia until you act on it

That and the legal age for boning is 15 in Poland, so I don't see it as a big deal.

And while I don't see them as a couple at all, I really don't get where people get the hate vibe. Rikku is nice to everyone, as has been pointed out, while Wakka is torn between his racism and enjoying Rikku's company. He clearly tries to be nice in spite of himself.