I am not easily offended and was not offended by your comment, and stand by my statement that you should always give full disclosure when selling or giving a live animal someone else is going to have in their care. I don't care how common, if you know your animal has an illness, or is a carrier of something, or their line has congenital issues known to you, you should disclose.
I thought my original comment was clear I knew how common it is since I said the flock would likely be re-exposed w/o complete isolation from all of outdoors.
The best approach would be not to share from a flock that has had sick birds. That would be the common sense approach. In this case, there should be no birds being discussed.
There is no way that I would share any bird that I thought there was even a chance of spreading something to another farm. I would not take the chance, so there is no necessary discussion to be had.
Respectfully, you still do not get the full point, but I will concede the point.