There are so many things someone can say to a woman while she's breastfeeding that supports her decision and her body's ability. I mean, let's be real: breastfeeding isn't necessarily easy. It's taxing and sometimes painful and usually exhausting and while it is beautiful and amazing, it's also difficult, especially when our society continues to shame it. If you're a cisgender man who can't experience breastfeeding for yourself, you can still help assist the women who can. If you're a grown-ass man, there are things you'll refuse to say about a woman's body while she's breastfeeding, because you'll be acutely aware that women's bodies have been sexualized to the point that the functionality of a woman's breasts falls second to the sexuality of a woman's breasts.
I was lucky in that I had a partner who not only supported by choice and ability to breastfeed, he emphatically fought for it when we were in public and I was feeding our son without a cover and enduring the looks and judgments and inappropriate commentary of others. He made me feel like I wasn't alone in my breastfeeding efforts, and I can't tell you how helpful that was. The more grown-ass men come to realize that even if they can't breastfeed, they can still be part of the breastfeeding experience and do things that support breastfeeding, the easier women who choose and/or are able to breastfeed will have it. The more grown-ass men help breastfeeding mothers, the more babies will end up benefiting from breastfeeding, in general.
So, in the name of supporting breastfeeding and the mothers who choose and/or are able to do it, here's a list of what a grown-ass man (or any man, hell any person) should absolutely never say to a woman while she's breastfeeding. Sometimes, the best way to learn how you can help is to learn how you could potentially hurt, and adjust your actions and statement accordingly.