I realize pg has pretty much abandoned this forum, but I admit I was still surprised to see him recommending Clojure instead of Arc in the above tweet.
I'm sure part of that is that he doesn't right now want to deal with people making requests for it. And having a userbase would mean that.
Off topic: I don't know how to encourage Arc. I don't even manage to follow the forum. What I know though is that I want Arc to exist. It's a huge mental relief to know it exists.