y not said, “If A hurts B, then it would be B’s turn to hurt A in this life or in a future one.”
It does not normally work that way, even though it can happen in some specific cases.
Especially in “samphassa ja vedana”, it is not due to a specific kamma. As the name says (“san” + “phassa” rhymes as samphassa), it arises due to “san” (lobha, dosa, moha) that is in one’s mind as one’s gati.
“Samphassa ja vedana” is explained in the post, “Vēdanā (Feelings) Arise in Two Ways“, as I mentioned earlier in the discussion.
It is imperative that one must understand the key concepts:
“Key Dhamma Concepts“. This is a general comment, not directed at anyone in particular. I have no way of knowing who knows how much.