I believe the most important thing in communication is understanding the comprehension capabilities of the recipient(s) of your message
It does not matter whether it is listening, speaking or writing.
You should always tailor your communication to your intended recipients. This could mean using whatever that works best.
To some this could mean good grammar, different accent, different language, and even vulgarity, if necessary, to get the message across effectively. Sticking the middle-up has been a effective and accurate way to communicate one's negative feeling since Roman times to today's road-rage situations. I am not suggesting that we transmit such messages, but just illustrating some other effective communicating tools that is available out there.
Some messages can best be transmitted by a movie, an experience, expression of a feeling, theatrical performance, a song, a piece of art, and even through a fable. Jesus, a great teacher, used parables to effectively communicate complex spiritual concepts to the masses.
It is responsibility of the recipient(s) to apply all due diligence to understand the message they receive.