PG isn't warning any experienced Common Lisp programmer about `nconc`. The [n] at the front means it's destructive...there's also `nsubst` and `nreverse` and `nstring-capitalize`. They all exist in Common Lisp to allow a programmer to avoid consing and the subsequent garbage collection. In other words, they exist to allow a programmer to optimize their code. They exist as exceptions to idiomatic Common Lisp practice of returning values in lieu of mutating locations. Sure it is not as idiomatic in Common Lisp as in Clojure in part because Common Lisp is largely a product of its time and that time was largely single threaded.

Avoiding mutation in Common Lisp is even less idiomatic than it is in Scheme - where there are not destructive versions of various functions by default and idiomatic practice is mutation is signaled with a bang [!]. But again, the preferred approach is persistence and writing side-effect free functions. Indeed at the front edge of Scheme, Racket implements immutable data structures by default.

Idiomatic functional style and defaulting to immutable data structures are not what makes Clojure unique as a Lisp - it's knob twiddling, not a new paradigm. It has some great built in syntax that allows for the best part of Lisp-2 programming - i.e. symbols representing a collection acting as functions over the collection and the association of a meta-data map with a symbol like a plist. But it's evolutionary as a Lisp.

On the other hand, though not unique, idiomatic functional style and defaulting to immutable data structures are unusual in relation to the Java platform. Its relationship to the Java platform is what makes Clojure unique. STM is not a product of it's Lisp heritage. Neither is it's implementation of objects with via interop [largely eschewing objects despite availability is also idiomatic Lisp].

Understand, I'm writing to think. What you've written is just a starting point I can use as an excuse for saying what I was primed to say anyway. Like I said in my original comment, I was already drinking from the Clojure firehose.

So what's the upshot? Well what did your article say that hasn't already been said before about functional programming? Why not point people to Chapter 3 of Graham? It's more convincing for those who need convincing and more in depth for those who don't. Why not point people to The Value of Values, it's again more convincing for tire-kickers; a comfortable sermon for the newly converted, and a reference point for those already in the cult.

What really makes Clojure unique?