A repeat offender in this situation would refer to people who are operating based on something like a three strike system (as in they can get in trouble three times before they’re removed) and used up the other strikes before using up the last one by being in trouble for upsetting the person in question who later has a change of heart. In this situation, you could surmise that, since the last strike was unfairly used up, you could undo it and let them back. Or you could think “well, it kind of blends in the other two strikes and how those past rule violations fairly used up those strikes”.

A one-chance policy would simply be the opposite of that. That’s where you say one rule violation seals one’s fate.

The specific example doesn’t have to be deceptive in nature. Suppose the way in which the “John” corespondent violates the boundaries of the “Jane” corespondent is to make recordings of the latter or challenge their conception of privacy. Or maybe one verbally offended the other. These are not what one would call universally set lines. You remove the offender, but later their removal is lamented. “I am sorry but I want to revise those lines [which would be in favor of the John correspondent who may come back if you decide they can]” the Jane correspondent says. And technically you could have an analog to this that doesn’t need all those people; people go to jail all the time for breaking laws that get removed a month later, to demonstrate what level that can work on. It’s here the question of what to do lies if it were up to you. Not that I’ve ever met an honest Jane.