I actually agree with the main point. In every one of the examples, however, the person who spoke isn't thinking about communication, but about himself.

"Water no cold!" may result in snickers amongst the wait staff, and they may not even understand. "Water, no ice please" is certainly more respectful and appropriate. Simply saying "confirmed" is easier for your agent, but it may insult the recipient by being so terse.

Use good grammar with acquaintances to show respect and professionalism. Use your own style with people who know you well to show your personality.