I noticed on my last few confirmations that Marriott emails are surrounded with single-quotation marks. Example:

'Marriott Hotels & Resorts Reservations'

The problem is if you sort your email by sender, then these don't properly appear in the M's. Pending this being fixed, I'm giving Marriott the benefit of the doubt and assume this is an oversight rather arrogance in assuming their e-mail should sort before everyone else's email.