Earlier quoted context omitted.
> Namely, tracking the duration a user is probably giving their attention to a given item, I pay a lot of attention to classes of things I don't want to see at all .
Then, according to the algorithm, you do want to see them.
That's exactly the problem! I don't want to see them, but the algorithm refuses to ask me.
If they think that the length of time I spend on a post is 100% correlated with the amount that I want to see it, they really don't understand people at all. It's an embarrassingly shallow model of how how humans behave.