"sufficiently tentative and ambiguous to allow him to act as if no initiation has been intended, if it appears that his overture is not desired."
Which makes sense. It's a good way of saving face. Rather than being a person other people ignore, you can just say their thoughts were on other things. Letting people save face is really important if you want to keep them happy.
Howard Rhiengold in his book Smart Mobs gives a good example of text messaging being used for this. He talked about kids in Sweden after a party. Say you've seen someone you quite liked and you'd like to see them again, but don't know if the feeling's shared. You'd send them a blank text message, or maybe just a really bland one like "hey, good party". If they reply, ask for a date. The first message is almost entirely expressive communication: tentative, deniable.
So what usually happens in cyberspace, if I want to approach someone? I could send them an email to see if it's okay to start emailing... it's all quite blunt, and although I can be tentative in what I write in that email it'd be better if it was built into the software itself.