Anonymous4: Lore-wise the sylvari copyed humain anatomy in form (heck they eaven have blood vesels, but they are filled with golden sapling). As the wiki said, they can have sex but has no reproduction. They most likely have nipples. No reason not to have any.
Anonymous6: What is the purpose of even having breasts if they don't have nipples? And what's the point of generally covering them up if there's nothing on them?
Also, it's porn, who cares if the anatomy is right?
Anonymous7(2): It was confirmed by Ree and Krystin Perry that they have breasts because they attempted to copy human anathomy, but they have no nipples. Go google it :). You can also look at Male sylvari models - none of them has nipples. It was not explained why female sylvari cover their breasts.
Anonymous8: In the start of the development circle for humans, they are not defined as gender, and nipples are made. Then, the human embrion gets a gender but keeps the nipples if male. If the sylvari were born from a tree, then they have a different development circle. Hence the reason for no nipples on male sylvari. I could not find proof that what you say is true Anon7. (google)
Also, it's porn, who cares if the anatomy is right?