(I think this one came in response to a point I made about whether a spouse can claim to have forgiven his or her adulterous spouse, and then divorce him or her at a later time and claim to have the right to remarry. See: "If a woman accepts her husband back in desperation, can she later divorce him?" )
Is it inconsistent for anyone to say they forgive another, but then continue to hold them accountable to the debt created by the sin? That is exactly what God did to David in II Samuel 12. In one verse Nathan told David that the Lord forgave him (II Samuel 12:13), and then in the very next verse he told him that God still held him accountable to the debt created by the sin - that he must still suffer the consequences of his sin (II Samuel 12:14).
I'm standing in as a third party in this exchange, so forgive me if I get some of the details wrong.
I think there is a problem in identifying divorce as a punishment in Matthew 19 and other locations. The divorce "option" is not there as a means of punishment for one party or the other. It may logically be thought of as a consequence, but it is not actually a punishment. In order for divorce to be a punishment, it would need to be required or at the very least be considered the most viable option. In Matthew 19, Jesus is minimizing it so much, that we have to work at the sentence structure in order for it to stand out enough so that we can argue over its meaning. In my mind it is clearly meant as a concession, a recognition that some conduct and betrayals are hard to reconcile.
In addition, the concept of forgiveness and consequences do not necessarily coincide. I think II Samuel 12 is an excellent example of that. David was the one that sinned, yet it was the child that died. The child obviously died at least 9 months after the adultery was committed. The only reason we know this was a consequence of the adultery and murder is because Nathan told us. It is not a natural consequence. It is one that God inflicted -- after telling David that he was forgiven. Also in Numbers 14, the children of Israel are forgiven by God and then he tells them that they are going to rot in the wilderness for 40 years and none of them were going to enter the land of promise. Pretty stiff penalty for having already been forgiven.
The same can be said about many sins and crimes. A murderer can ask for forgiveness from God and the victim's family -- and they can all grant it, but that does not mean that the consequence of the sin (execution) is put aside because of the forgiveness. One of the consequences of committing adultery is that your spouse can put you away. Jesus did not set a time line. He did not impose a statute of limitations. He did not impose conditions of forgiveness, non-forgiveness, penance, time off for good behavior, or any other caveat. To insist on any additional clarification in the matter would be to add words to what Jesus said.
Now, as a matter of wisdom, I think it is possible to debate various options. I would agree that the longer the time between the admission of guilt and the request for divorce, the harder it will be to connect the two events in my mind. However, it is not my mind that you have to convince. You have to convince Jesus that the two are connected. He will actually understand all of the hidden details and he will make a righteous judgment in the matter. We just have to keep in mind that when he offers up his judgment, it will be final and there will be no time available to get it right, make amends or undo the choice that we made.
Suppose, for the sake of discussion, that a wife cheats on her husband just one time. Ten years later she admits it to him and twenty years after that he wants a divorce because of the adultery. The immediate reaction of all normal observers is to say that the husband is just using the past event as a cover for something else. As an outsider we would feel completely justified in claiming the divorce was not allowed. But what if the reason the husband is asking for the divorce is because the wife continues to mention "John" while they were in disagreements. For example she might say "I should have stayed with John 30 years ago". How does her current conduct reflect on the events of 30 years ago? I personally do not want to be the judge in such a situation. However, I can easily see with the added information that the wife has not repented and likely was not even sorry for her past conduct. Regardless of if the husband had forgiven her, she has made it extremely hard on him to live with her.