i don't think it counts as mature, seeing how the naughty bits aren't included
That would be like saying any cartoon involving Donald Duck or Buggs Bunny is mature material because they are male characters who lack pants o.o

I don't think it does, but I would put it in there anyway to be on the safe side, personally.

The second part of this would be on Comicfury, and that if I posted it on my webcomic's page I might have to flag my comic for nudity because one image that isn't even a part of the comic contains female breasts. Albeit without the nipple. And I don't want to have to flag for nudity.

Just draw it covered or censored or something so you won't have to flag nudity.

I did. Already put it up. ;o

Oh, I see.

Alot of people dont mark it as mature but so do. Its kinda 50/50 but mark it as mature so there wont be any problems <3

what exactly makes nipples mature?

Because the world is full of prudes...

And erectile tissue or something...

The FA ratings are pretty lose... what I see most artists follow, as a general rule of thumb:

nothing showing (including fur covered breasts and crotch showing no nipples or genitalia) is 'clean'

nipples or genitals showing, non lewd pose is mature

lewd pose (ie: spreading of the vagina), presence of sexual fluids, or sexual activity is adult

in general, again, some artists err on the side of caution and just mark everything above what they consider a clean G rating as adult.

No nipples, not mature. It's just cartoon nudity.