Forums usually have rules posted. If you do not follow the rules, it results in either one warning or banishment from that group. Perhaps it was not the right group to be in if someone gets banned. I would move on.
Family. You can’t get banned from family. Family is blood and is forever. You can get ostracized from a family, or simply choose not to associate with them. People do tend to grow in different directions, with different life objectives, so limiting your association if that happens is probably a good thing.
Country. Being banned from entering a country would mean you have a past that is not acceptable, or perhaps just a ban from your country of origin. I would think twice about wanting to go into that country and move on with my life in another country.
A survival group. If someone was banned from a group, it would be because their believes, views or goals do not mesh with the group. It would be done for the good of the group,… hopefully anyway. If I was banned from a survival group, I would think I would know why or what I did to deserve it. Hopefully I would learn from it and either pick a better group or at least not make the same mistake twice.
A church. Being banned from a church would mean I had done something against the beliefs of that organization. I would hopefully know what or what it was. I would move on and pick a church that was better suited to my beliefs.
A social Club. Banishment from a social club is a different animal. There does not have to be a logical reason, and I may never know what I did or who did the banning. Social groups have a lot of grey area rules and emotions drive them. If it was a group that had meaning to me I would try to find out why and remedy the situation. If not, I would cut my losses and move on.
If you are referring to the join dates of some members here. Yes. I personally was not banned or ostracized from the forum. That particular Forum started to go in a direction I did not care to participate in, So I left and moved on.
You mentioned Trolls. To me a Troll is someone whose goal is to stir up trouble. They live for finding a group, any group, and posting dissenting opinions on everything. If it is a group I am a Mod in, I have a little private talk with them. If they persist I ban them. I see no reason for someone to join a group they have no interest in, or have the complete opposite opinion of, and start posting there. It is a big web with lots and lots of forums. Find one with your goals, opinions and likes, join it and be happy. I can’t for the life of me understand why anyone would waste one minute of their life with any group that they had no interest in or anything in common with. It would be like joining a garden club when you are a couch potato. They meet, outside, at a different garden each week and you go there and complain the whole time that you are missing all the good TV shows. Perhaps they feel if they go to each meeting they will convert them from gardening to couch potatoism?