Earlier quoted context omitted.
You've been able to do this in Ruby since I can remember. Not a lot of editors take advantage of it though...
No. There is real, palpable, practical, functional difference between working a Lisp REPL and a REPL in a non-homoiconic languages - Ruby, Python, Haskell, etc. Every single stage there in Read-Eval-Print-Loop differs. Man, it gets so exhausting trying to convince every PL critic who grabs a single (or a couple) of axis of any language and tries to dispute the value of a language without ever understanding the holist…
I used Clojure when it first came out, I've used Common Lisp for years, I've also used languages like Smalltalk and many others.
Yes, Lisp environments are nice, but sometimes I think Lispers are so insular they don't realize that other languages have similar things. R, Julia and Ruby have similar environments. Smalltalk is next level.
And homoiconicity is great for macros and parsing but it's late-binding that enables the live programming behaviour, which isn't exclusive to Lisp.
Also if you'd ever gotten deep into say, SB-ALIEN, you'd know the limitations too; Common Lisp isn't magic, it can't just redefine say, instantiated structs in memory. It relies on pointers then switching references on the fly.