This might be more of a blogosphere-era thing I guess. Even when most people blogging did it for pleasure rather than work, it was always considered polite to “hat tip” (h/t) the source of a given link, if you happened to find it on someone else’s site.
I see this claim so much, and it’s bullshit. Harris didn’t make a single policy concession to get Cheney on board. And why would she? The entire point of having her endorse was to send the message of “Trump is so dangerous that even people who disagree with me are choosing to support me.”