I definitely don't consider Lucky Star a kiddie anime. It might look or be stylized that way, but the content is definitely not so. I guess it all depends on your definition of "kiddie"
IMO, kiddie anime is all about content. I don't think action and gore is a prerequisite for that label. There is a lot of anime that doesn't have either that would be considered "adult/mature anime".
I think the point being that the original poster and probably alot of people looks at the anime style before the content to decide for themselves if its kiddie or adult. Like again what was said before. Take Higurashi no Naku Koro ni.. You look at the cover of the anime/dvd

Then whats the 1st thing that would come to mind?? Kiddie Anime. From all I take of it the only themed as he puts Adult would be anything dark, with continuing fighting, foul languages, and immense death scenes.
Reki
Well... I don't know if the Higurashi cover's a horribly good example, considering there's a medium-sized blood splat right on the title, and it looks pretty damn creepy, no matter how you look at it...
But to be honest, I understood mostly what he was saying when he said "kiddie anime" right off the bat. It's just "mature" anime. It's hard to explain, but it's not that hard to "feel". The style of the artwork, the storyline, etc. All are attributes that help define what is and what isn't a kiddie anime.
I'm not too sure where I would place Higurashi. Now that I look back at it, it all seems like a bunch of disconnected violent shit happening (with an overall "friendship" theme, to top it all off......). It seems more like it was targeted to the 15-17 year old range, with maybe a slight cult following in the 30+ pedo age range.
I mean, I definitely wouldn't place
Seirei no Moribito in the "kiddie anime" description.