You would THINK that a punctuation mark used as often as the comma (especially when you consider how powerful it is) would be used correctly and with agreement, but you'd be wrong.
That's the (alleged) paradox — usually we get better at using things we use a lot, or usually we're careful about using things that have a lot of power, but that's not so with the comma.
I enjoy cooking, my friends, and my cats. -- I have a hobby.
I enjoy cooking my friends and my cats. -- I'm a cannibal!
Student or Learner