Breast milk is not a fixed product. Rather, the suckling action as well as pathogens present in the baby cause it to change its composition. It contains antibodies for the baby if the child is sick, and its fat/sugar ratios change depending on the age of the baby (via suckling). Pumping removes this feedback loop from the mother. There is little research here, but preliminary research (https://psmag.com/economics/unseen-consequences-pumping-brea...) demonstrates several negative effects of pumping. Pumping often produces too much foremilk (high in sugar), rather than hind milk (high in fat), because pumping doesn't work in the way baby's mouths do.

As for comfort. I think most babies are comforted by feeding. However, with formula, you have to be careful not to overfeed. You can't really overfeed with breastfeeding. The maximal amount of calories the child can get is whatever amount his mother is eating, so if mom is eating the right amount, the baby will get it.