We did it on a Legend repositioning cruise for Alaska in 2015, before starting her season in Seattle. The other time we did it was on a Princess one way Alaska. Hands down the most scenic port when you sail out with land visible most of the night.
I've had it work with facebook messenger in the past, pre-starlink existance. It seemed like it would happen overnight where I would receive the messages for the day, then replies to those would go out the next night. My guess was they allowed many things through in a window where they opened up service due to one system process or another overnight daily.