It's been at least four years since my MR account did NOT post a paid night or points. The last two stays, I am 0-for-2. I think I have a theory - - ->
Both of these stays had my reservation as checking out a day after my actual checkout date (no folio under the door tipped me off on needing to visit the front desk). At the front desk, I formally checked out, received a hard-copy folio (which I validated had my MR account #), and asked for validation of my e-mail address. Never-the-less, neither of these stays posted nights, points, nor did I get an e-folio via e-mail.
Could this explain "the most common scenario" where other MR members report not getting points or nights posted?
Ping -- I also always check out at the front desk, and quite often a day or two earlier than what I had originally checked in for. I haven't had a problem getting points posted in several years, other than the 500 welcome gift points at the MCO Marriott a couple of months ago. I just haven't brought myself to trust email enough to depend on than for my proof of stay. Maybe the efolio is not really as big a deal as it seems to me.
Ping -- that's just my experience, but more to your point, you may never find out the root cause. My experiences in the pastn usually led me on a snipe hunt with the hotel blaming MR and MR blaming the hotel. And, of course I didn't give a rip whose fault it was, just fix it!
I may have spoken too soon about the Venice Courtyard. I checked out Tuesday morning and it still hasn't posted to my account. I know we're expected to wait two weeks before calling, but in my experience if it's not there in the first three days it tends not to show up without phone calls and faxes.