Personally, I nurse from the top of my shirt. There are various reasons for this. I've never thought anything of it until seeing it mentioned on a couple online forums as unnecessarily immodest. Honestly, I've always considered myself to be a fairly modest nurser (in spite of the fact that I never use a cover) because I'm only exposing a tiny bit of skin by pulling my breast out of the top of my (already low-cut) shirt, rather than exposing my whole mother-worn tummy area by pulling my shirt up to pull my breast from the bottom. I take care to cover my nipple until she latches. Once she is in place, her head covers my "exposed" breast area... and actually reveals less skin than before.
This, exactly. I don't wear a bra either, preferring snug camisoles under my shirts. In theory I could lift the top shirt and struggle to get my breast out over the top of the camisole, with the top shirt hiding my upper chest, but why? A screaming baby impatient for milk draws way more attention, IME, than a mother quickly and quietly pulling a breast out of the top of her shirt and latching the babe on.
I'm a shameless nurser and I don't care who sees. I don't go waving my breasts around, and if the baby is distracted and popping on and off a lot, I do take some care to keep my body sort of covered up, but I don't really worry about NIP exposure. My baby is hungry and that is my first priority as her mama. People who don't care to see (part of) my breasts don't have to look, but I'm not about to skulk around in shame or hide my poor babe's face under some stuffy blanket, not least of all because that's not the example I want to teach my children about breastfeeding.
There's nothing dirty, obscene, or sexual about breastfeeding and I refuse--refuse--to let other people's discomfort affect my nursing relationship with my babies. Yes, I think some women bare a little more than strictly necessary, but then again, it's not up to me to decide what's necessary and what isn't. My opinion means nothing compared to their child's need to eat. If mamas want to cover up or nurse topless, I don't really care. It's not my own cup of tea but again--my opinion doesn't matter! Baby needs to eat.
By the way, as open about it as I am and as many places as I've done it, I have only ever been shamed for nursing in public once--it was a 20-something guy, some distant relative, making a crude comment when I was (very discreetly) nursing DD at my grandmother's house after my grandfather's funeral. The guy's father shut him up right quick with some very harsh words, and then told me that there's nothing more beautiful than the sight of a mother nursing her baby. I will always love him for that.