The CTO, Clifton Cunningham, did help by giving us the space to create new things. For example we also work on our own Javascript library for building the in-house CMS - https://github.com/MailOnline/milo
However, Clojure (we also use Node.js BTW) really does work for us. In the 11 months since Jon's blog post, the code has grown (I guess 30-40k LOC across several processes) but it also does much more too. I think Clojure helps because it gives more freedom to refactor/factor the code in the way the team want.
For example a decision could be made to create a microservice for a commonly used URL or API. Sure you can do that in other languages, but it just seems easier with functional languages, I think because the composed functions seem easier to lift and shift. I've no evidence for this, just gut feeling. I spent years doing Spring/Hibernate etc and really don't miss it.
We'll definitely continue to support Clojure and other functional languages.