As a normal course of action, I try and add my MR number into any II exchange or getaway when they are first booked. I am 50/50 on being successful and the reason I do it is to see the reservation in my online account. An interesting thing recently happened. I exchanged 2 non Marriott banked weeks into consecutive week stays at the Surf Club. Circumstances required me to cancel and re-trade one and the other I let my brother-in-law and his wife use. I actually switched it to their name as not to have a problem.
a few days after the first week was over, I noticed 7 nights were added to my night stays. I looked at the reservation for the second week that was in my account and it showed the name of my brother-in-law and had in progress. After it was over, I did not get credit for that stay.
The credit rules as stated requires the MR member to occupy the room to get credit so I should not have gotten credit for either. This was the first time this has happened so I was curious and willing to loose the 7 nights in order to understand what happened. I found the II confirmation send for the first week, copied the MR reservation number and called Marriott. It appears that the Marriott reservation stays with the unit no matter how many times II confirms that week. Since my number was added, unless the new occupant adds their own MR number during check in or out, my MR number stayed with the record. The MR reservation actually had the new name and my number. My bother-in-law is not a Marriott member so my MR number stayed in the record also. The Marriott person said this is the reason exchanges (or getaways) are not suppose to have the MR number put in until check in.
I asked the person from Marriott Rewards why would one go through not the other. I was told that it should have been caught by the resort both times and if not the resort, an automated process. He didn't know what happened to allow it to pass both checks. I was going into this expecting the night credits to be taken away but he did not.
I asked if I rent out my week that I own, do I still get credit. I know the answer was no but I asked the question anyway. The answer was no. I rent my HHI unit frequently and I have always gotten credit. In my rental agreement, I put in the MR number will not be replaced. As of now, no one has replaced my number. Not sure why I get the nights credit but I won't complain. I didn't ask him to look into this.