I wasn't eating paleo when I was breastfeeding either of my children as young babies. I'm still breastfeeding my second at 14 months and I breastfed my eldest until he was three.
I don't think it's the mother's diet so much as the baby's diet that makes the difference in terms of poo. The biggest factor is whether the baby is exclusively breastfed - breast milk is the perfect food for babies, and easily digested. As long as the child doesn't have food allergies (which it may be getting exposure to through breast milk), there shouldn't be problems with poo while exclusively breastfed. It's normal for young baby poo not to be solid, but that's difference from diarrhoea.
Neither of my boys have ever had any problems with constipation, but both had a diet that was almost exclusively breast milk until 12 months. Babies seem to have trouble once they start getting rice cereal shovelled down their throats or fed formula. I should add that neither of my children had solid poos until they were over 12 months, but this was directly related to their high-liquid diet!