You may have skimmed my postI think he means quarantine as in separate a sick chicken from the flock as is widely recommended on BYC.
That is different from quarantining a newcomer to the flock who might bring in disease.
like I said, because chickens hide sickness by the time we notice a sick bird, if it has something contagious then it may have already spread. And if the others are fine, then it's not contagious. Either way, leave sick birds with their friends.

