If you have MS Office, check for these "Connected experiences" settings.

I could not access the settings using the instructions in the shared post, but I did find them by accessing PREFERENCES and searching for "connected." And, yes, they were already enabled. (Bad, Microsoft, very bad!)

Bonus: Turning this off in Word gets applied across the MS Office suite. (I checked Excel and PPT after changing the settings in Word, and they both have the connected settings toggled off).