Just to be clear, the search would not be on FT but on the MR database itself. Not claiming to be an expert, but I have done very similar things in my job when merging DBs and purging duplicate entries. Searching for accounts that have received stay credit for more than one night on the same date is pretty straight forward.

And pointing out MR does not follow their own T&Cs on a public board could be just the incentive needed for someone like Marriott Concierge to put in a request. And since MR "owns" the account, they are within their rights to close the account and you can be out nearly half a million points (a minor reduction in their liabilities).

As always posted on FT YMMV, so just because one event happens, does not a policy make.