Exchange 2010 introduces a Calendar Assistant, which can be handy for automatically marking incoming meeting requests a tentative, and other very handy functions that can execute out side of the client side experience.
In this one particular scenario, embarrassingly, was my own mailbox for a few days.
I had no control over meeting requests. They were getting rejected and accepted without me ever seeing the request come in.
I checked my phone for any strange settings.
I checked over the Calendar Assistant and disabled it completely, from the Outlook Web App control panel and in Powershell just to make sure it was "super disabled".
Calendar items kept auto-answering for me so I had to dig deeper, into a section I rarely go into unless the mailbox is setup as a resource.
Lo and behold, somehow and at some point, all of these items had been clicked on within my Outlook profile.
I don't know if I did this on accident one night or my kids got into my Outlook settings (never underestimate the comedy gold that can come from smart 8 year olds) with that said:
As you can see, these options were what was killing my Calendaring. Very "stupid user" to not check this spot first but it was originally acting like something the Calendar Assistant was doing and I had forgotten about the resource room settings being buried in Outlook 2010.
So, I got to wear the dunce hat for the day. Maybe me posting this will avoid some other dunce hats getting passed out to others. It was definitely a 'palmface-slap' moment when I discovered the root cause.