I checked, easy comms is enabled in the MP set up, I don't recall seeing this format xx.xx when playing single player with easy comms disabled so I'm just going to assume it's a glitch.
I usually use the 'M' slot on the radio for inputing my desired freq., sometimes I overwrite the other pre-loaded channels 1-20. Never understood why pre-loaded channels were not installed in numerical order?
I recall there used to be another comm command when on the ground whether parked or taxing besides what you mentioned. It was needed until you were airborne, don't currently see it as an option.
Would you know what these commands do?
COMM 1 Antenna Selector Switch - AUTO
COMM 1 Antenna Selector Switch - Down