My server (Mind Trick) still has plenty of chatter in general, not all the time, but a good deal of the time. In my years of gaming though, I don't think I have really seen people respond in a non-sarcastic manner to someone just saying "hi" in general unless the people responding already knew the initiator. If you want to start a conversation, you have to draw peoples interest.
If you walked into a crowded room full of people you don't know IRL and just shout "hi" to the whole room you're going to get ignored (or in mmo's /ignored).
If you walk into a room of people you do know, and shout "hi" you can expect a response, same goes for guilds and social chat channels.
If you want to just shout into a crowded room and get a response though, you have to shout something that makes people want to continue a conversation. Ask a question, make a statement, tell a joke, give people some reason to want to talk to you.