One thing that brings me back to conversations on Facebook are the notifications. With so much content coming at me from all sides (not to mention real-life commitments), realistically I will not remember to revisit an interesting post to make a comment I couldn't initially make or check for new comments unless there's something to remind me. So I use the Turn On Notifications function on FB a lot. I know a similar function is available on DW, but it was never part of my DW/LJ flow. I'm now trying to use it more (after a period away from DW). You could perhaps highlight the feature in the Salon intros so anyone who's interested can turn it on and get those little remindery pings to come back and read new comments or add forgotten ones.