Has something changed about the community such that we're now at http://app.slack.com rather than http://clojurians.slack.com?

I don't understand the question. You sent it to http://clojurians.slack.com, did you not?

That is where I read your question

Hmm. I must be being split test. When I go to http://clojurians.slack.com, I'm redirected to http://app.slack.com