I used it a few times in a row, posting different ones of my bookmarks (for example, Isaac Asimov's Last Question and Last Answer stories), and at one point got my own link back.

Due to the low-quality links I always got before that I had first assumed it was just... garbage, but it seems it's just the users.

UPDATE: I've now tried about a dozen times (each time providing a link that isn't porn and contains informational content), and got 9 porn links, 1 racist site, and 2 actually interesting links, one of which seemed to have been added by an HNer: contentful.com