Seems worth mentioning that the four ways you list for events to be causally linked are the building blocks of d-separation, not the whole thing. E.g. “A causes X, X causes B” is a causal link, but not direct. And “A causes X, B causes X, X causes Y, and we’ve observed Y” is one as well. Or even: “A causes X, Y causes X, Y causes B, X causes Z, and we’ve observed Z”. (That’s the link between s and y in example 3 from your link.)
I am using the word “causal” to mean d-connected, which means not d-seperated. I prefer the term “directly causal” to mean A->B or B->A.
In the case of non-effects, the improbable events are “taking Benadryl” and “not reacting after consuming an allergy”
Seems worth mentioning that the four ways you list for events to be causally linked are the building blocks of d-separation, not the whole thing. E.g. “A causes X, X causes B” is a causal link, but not direct. And “A causes X, B causes X, X causes Y, and we’ve observed Y” is one as well. Or even: “A causes X, Y causes X, Y causes B, X causes Z, and we’ve observed Z”. (That’s the link between s and y in example 3 from your link.)
Oh yeah, definitely agree!