Inbreeding is rife in both egg and bird sales. I could make a fair bit selling hatching eggs if I wanted, take the Thuringians for instance, they take a lovely photo and if anyone visited they would find them lovely birds. I did have a cockerel who was brother to my girls, if I had kept him I could have sold fertile hatching eggs which would be inbred but by the time the faults become apparent it is a year on and too late to take issue, if I'm selling on eBay then I would already have positive feedback from the buyer. With regards to selection I'm not so sure how a cock selects his favourite hen, the Count has tread both of my black Araucanas to the point that I have had to fit them both with saddles. They are his hatch mates, they also have sight issues which makes them easy to catch but I think it is based on fertility more than anything, he treads one of the exbatts that still lays and studiously ignores the non layer.