And the high OBLs, man, to blackhat niches.
One flag almost nobody checks: the history of the donor site itself. I look at 2-3 years of Wayback. If the site recently changed topic or language, or was a placeholder, and now it's suddenly an "authority blog" with hundreds of posts, it's nearly always a rebuilt drop set up to sell links. I also check whether traffic grew gradually or jumped in a single month.
Agreed to the fullest. It is more important to have clarity rather than an exaggerated claim about DR value.
Those you already mentioned and even indexability. I remember a seller promoted a very high DR site with good traffic to me, only to realize that the pages on which my links would be placed would never be indexed nor would they even rank. There are many scummy practices these days.
