As a young father with a wife that loves wine, we have thought about this a lot. Surely, moderation is always good advice. But at the end our reasoning was the following:
If a nursing wife drinks wine, the alcohol will get into her blood, so it will end up in the milk eventually. If we assume that the alcohol is not accumulated in the milk, the milk should not contain more alcohol than the blood. This means for moderate drinking something like 0,02% alcohol contents in the milk as consumed by the baby. If you compare this with the possible alcohol contents in e.g. apple juice (up to 1%) or sourdogh bread, i don't see a dramatic problem. Of course this very slightly alcoholic beverage for the baby is then metabolized and will probably have no effect on the blood alcohol level of the baby.
The situation is of course different for pregnant women, where the foetal organism is directly connected to the mothers blood circulation system and thus (simplified!) may have more or less the same
blood alcohol level as the mother.
To sum it up - of course I don't advocate heeavy drinking but I don't have a problem if my nursing wife has a glass or two with dinner.
But what di I know - I am only a physicist and not a physician.
Regards, Robert