Add this, jws can as individuals marking an individual as bad association, but not telling others they should do the same (like that won't happen).
When a jw treated that way finally gets an honest answer from a jw shunning them, they find out it was because of another individual jw's (elder) opinion (which has spread through the congregation), it is not a congregation marking. I know a jw this happened in the late 70's and the elders told them that the elder was protecting his family from bad association. That person asked, they why were they telling others they should do the same? Nothing happened to correct the elder or his family who spread the word.
In some cases individual Christians must determine whether certain persons in the congregation are good companions for themselves or their children. (1 Cor. 15:33)
Consequently, marking should not be confused with a personal or family application of God’s advice to avoid bad association.