If you want to drive yourself crazy, read the live twitter comments of an audience after you give a talk, even if it's just to ten people.
You didn't say what they said you said.
You didn't mean what they said you meant.
Or read the comments on just about any blog post or video online. People who saw what you just saw or read what you just read completely misunderstood it. (Or else you did.)
We think direct written and verbal communication is clear and accurate and efficient. It is none of those. If the data rate of an HDMI cable is 340MHz, I'm guessing that the data rate of a speech is far, far lower. Yes, there's a huge amount of information communicated via your affect, your style and your confidence, but no, I don't think humans are so good at getting all the details.
Plan on being misunderstood. Repeat yourself. When in doubt, repeat yourself.