The subject of marking was always a bit vague. I only got involved in one case of someone who insisted on giving a Christmas present to her grandchild . Although I argued against it, the rest of the body of elders insisted . The following is from Watchtower 1999 July 15th p29 - 31 :-
Paul did not lay down detailed rules as if trying to create a complicated procedure. But it is plain that the elders should first counsel and try to help a disorderly one. If they do not succeed and the person persists in a way that is disturbing and that has the potential for spreading, they may conclude that the congregation should be put on the alert. They can arrange for a talk on why such disorderliness is to be avoided. They will not mention names, but their warning talk will help to protect the congregation because responsive ones will take extra care to limit social activities with any who clearly display such disorderliness.
Hopefully, in time the disorderly one will be ashamed of his ways and will be moved to change. As the elders and others in the congregation see the change, they can individually decide to end the limitation they have put on personally socializing with him.
In summary, then: The congregation elders take the lead in offering help and counsel if someone is walking disorderly. If he does not see the error of his way but continues to be an unwholesome influence, the elders may warn the congregation by means of a talk that makes clear the Biblical view—be it of dating unbelievers, or whatever the improper course is. (1 Corinthians 7:39; 2 Corinthians 6:14) Christians in the congregation who are thus alerted can individually decide to limit any socializing with ones who clearly are pursuing a disorderly course but who are still brothers.
I think it raises more questions than answers .