A reasonable gap there is. I am nowhere near as expressive in person as I am online, this has changed where I am starting to be more expressive in person recently and my friends were surprised. Then again I'm still nowhere near as expressive a person online as I can be.
This in every sense of the word has much to do with energy, when it is flowing for me I am an intensely passionate person, to the point I could have a big mouth, to the point where I am a mystery to the friends who once knew me from high school in every way, shape and form.

Would that be a repressed Fe/Fi, disconnected personalty, stress?