In my experience of life, my purpose in talking to someone was to communicate ideas. If you wish to transfer an idea, then you must be understood by the recipient of the idea. If you know the person well, you will have a commonality of experiences including language, slang terms and shortcuts of expression. In that circumstance it is appropriate to use these shortcuts and slang terms.
If I am speaking to a stranger, I try to use an even tone of voice, and restrict my vocabulary to words likely to be in common parlance. It is polite, and also my meaning is more likely to be understood. It shows that you respect the needs of the other person! I could speak in Dailect or use only Technical Jargon, but I choose not to out of consideration to my audience, and also because there is no point in me speaking if I do not intend to be understood!!!
My suggestion to the low(ercase)lifes who do not use any capitals or punctuation would be. Please treat ME with some respect! What is the point of wasting your time posting if we are going to automatically ignore unintelligible gibberish?
Quack!!!
GtD