Well, for a start, you could redesign the service so it's not just a mini-soapbox for each user...
I see his point, Twitter is designed in such a way that everybody does these little one-way bursts, and the only way to rise above the crowd and gain followers is to be more 'interesting' than everybody else, which will often take the form of being noisier, more outrageous, more controversial, more extreme.
OTOH, that seems to be what people want. I mean, there's already alternatives in existence. I'm talking to you in one now. People want a soapbox.
I think it helps that you don't have to think too hard about a tweet. Reading through a list of tweets every now and then is a lot less mentally taxing than catching up on a mailing list conversation.
There's certainly room for plenty more social network experimentation. The way Twitter and Facebook are designed shapes the conversation. What if you added common forums to Facebook? What if you just doubled the message size in Twitter? It would certainly change the way people used them.
Boy, it sure would be nice to have a free, open-source, distributed social network, so people could play with things like this more, huh?