Richard Kettlewell

That certainly seems like a much more reasonable claim. In particular, tone of voice can often disambiguate possible interpretations of a sentence which might be hard to choose between given just the words in text. Irony and sarcasm are one obvious such area, but there are more subtle cases too, such as emphasis – a de-emphasis of some particular word might indicate that it was intended as an illustrative example of the main assertion and not a constraint on its applicability.

Of course you can re-word to compensate for things like that, if you're trying to produce an equivalent piece of text, but it might come over very badly in a literal transcript.