The use of Chinese characters also serves to compact sentences. Since you don't have to actually spell out entire words, as in English, but can represent them with an ideogram, you can say a lot more in a much smaller space.
I will provisionally accept that kanji and kana make typing out written Japanese on a cell phone more efficient than typing out English (in the sense of requiring fewer key strokes; I'd have to test to see if this is really true), but I reject the logical fallacy that this mechanical efficiency leads to greater meaning.
This strikes me as a variation of a phenomenon Ben Zimmer over at Language Log has written about regarding the all too often misrepresented meaning of the Chinese word for ‘crisis’ wēijī . Underlying both of these is the naïve belief that logograms are inherently more meaningful than alphabetic words. This belief, I reject.
I could be wrong about this, but my hunch is that the human language system takes all written representations of language and converts them into an internal mental representation it’s happy with. There may be differences between the way the brain accesses the meaning of kanji and the way the brain access the meaning of alphabetic words (in terms of recognition), but I don’t see any reason to believe that the internal semantic representation of kanji is somehow different than the representation of words. If I’m wrong and there is a difference, this would be an interesting piece of data for the Sapir-Whorf folks.
FYI: The Sapir-Whorf hypothesis (aka linguistic relativity) has re-emerged in recent years. Some of the most interesting empirical work is being done by