Kudos to you on digging through their comments/post history. I see plenty of drama just looking at those that cross my path. From where I’m sitting, digging like so is just looking for the very things you claim to not want to see.
Me? I would rather fool around with my wife’s sister than all that, and/or hang out with those who do such things. If you can’t see the line between that and actual incest, its you with the blurred boundary issue. That said, my wife has no siblings, and I don’t need the drama enough to be sad about it.