Oh that's weird... I didn't realize they prohibited linking that severely... seems overly extreme, like... how would they even manage to keep that rule consistent? You can't link to any site that's EVER displayed an image of an erection, etc? Anywhere? Even if there's an adult-content warning page in front of it? WTH?
I'm NOT certain, but there's probably a know-it-when-they-see-it kind of rule in effect. I don't know the procedure, but I know of several artists who have had images taken down, or have had requests to change/remove images.
Oddly enough, DA actually has a pretty specific description of what they define as "pornography".
erections bodily fluids (real or simulated) manipulation/spreading of genetalia (hands, props, etc) penetration of anything sex toys only if made to realistically resemble anatomy
It's just their stance on linking that strikes me as way overboard... and having nothing to do with their definition of porn, there's just no way for them to possibly police every stray nook and cranny of every site someone's ever linked to... but their policy description makes it sound like that's what they're doing based on this FAQ article
To be honest, I have doubts that they police the off-site links at all... don't know how they would find the time to do that, given how much people complain about the supposedly months-long backlog on policy violation reports that have to do with content on-site. </snerk>