Spiteful for having your baby have your last name?

Sorry... small rant

Long story short, my boyfriend has been super unsupportive and cheated on me during this pregnancy. It’s gotten so bad that his parents are really upset with his behaviour and told him simply he needs to grow up. I said to him I want the baby to have my last name, since I will be the main carer and he’s shown no interest in being a parent or being around. He understands why I feel that way and said fair enough.

I wrote in another group if it was normal for baby’s to have their mothers last name and if there would be something he needed to sign to saying he’s okay with the baby having my last name. (This is my first baby, I don’t know how these things work).

And some woman replied and said she believes all children should have their dad’s name and that I shouldn’t be spiteful towards the dad otherwise karma will come and get me. But I don’t see how having the baby have my name is spiteful. He will still be involved with the baby if he chooses, I’m not holding the baby from him. I’m not sure how a last name involves karma getting involved 🤦‍♀️