"HP's Marriott code HPQ is one of the most widely shared codes in FlyerTalk's publicly usable Marriott codes thread. Marriott's automated system has been documented to disable Mobile Key for high-risk codes being used for the first time, forcing front desk interaction. HP's deep discounts — noted as cheapest in China by one source — make it a higher-risk code. Hotels in HP-heavy markets (Palo Alto, Houston) are familiar with the verification process."

"I am very rarely asked to prove my eligibility for a rate...but they have every right to ask and if you can't produce it, you will be re-rated to the current rate, which is often even higher and there is no guarantee points rooms will be available. Doing online check in rarely helps this as most properties don't actually do online anyway - especially to people who are not returning guests to the property or elite. You are taking a gamble. One that is likely to be fine. But understand you are intentionally breaking the terms of the bonvoy program and if someone really cared, there can be consequences."

"I don't do mobile check-in if I'm wanting to upgrade. I check the app before I go in to see if any suites are available to book during the duration of my stay. If there is I just say "Would it be possible to get upgraded to an available suite with my platinum benefit?". Of course this is typically at the hotel that I stay in about once a month for 3 day at a time for work. The front desk pretty much knows me and know that I am fairly low maintenance."